Python 2.4 Quick Reference Card



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Python 2.4 Quick Reference Card ©2005-2007 — Laurent Pointal — License CC [by nc sa] CARD CONTENT Environment Variables............................ 1 Command-line Options............................1 Files Extensions.......................................1 Language Keywords................................ 1 Builtins.................................................... 1 Types.........................................................1 Functions................................................... 1 Statements..............................................1 Blocks........................................................ 1 Assignment Shortcuts................................1 Console & Interactive Input/Output.........1 Objects, Names and Namespaces...........2 Identifiers...................................................2 Objects and Names, Reference Counting.. 2 Mutable/Immutable Objects.......................2 Namespaces.............................................. 2 Constants, Enumerations...........................2 Flow Control............................................ 2 Condition....................................................2 Loop...........................................................2 Functions/methods exit............................. 2 Exceptions................................................. 2 Iterable Protocol.........................................2 Interpretation / Execution....................... 2 Functions Definitions & Usage................ 2 Parameters / Return value.........................2 Lambda functions...................................... 2 Callable Objects.........................................2 Calling Functions........................................2 Functions Control.......................................2 Decorators.................................................2 Types/Classes & Objects......................... 3 Class Definition..........................................3 Object Creation..........................................3 Classes & Objects Relations.......................3 Attributes Manipulation............................. 3 Special Methods.........................................3 Descriptors protocol...................................3 Copying Objects.........................................3 Introspection..............................................3 Modules and Packages............................3 Source encodings...................................... 3 Special Attributes.......................................3 Main Execution / Script Parameters........ 3 Operators................................................ 4 Priority....................................................... 4 Arithmetic Operators................................. 4 Comparison Operators...............................4 Operators as Functions..............................4 Booleans................................................. 4 Numbers..................................................4 Operators...................................................4 Functions................................................... 4 Bit Level Operations................................5 Operators...................................................5 Strings.....................................................5 Escape sequences..................................... 5 Unicode strings..........................................5 Methods and Functions..............................5 Formating.................................................. 5 Constants...................................................6 Regular Expressions.................................. 6 Localization................................................6 Multilingual Support...................................7 Containers...............................................7 Operations on Containers..........................7 Copying Containers....................................8 Overriding Containers Operations............. 8 Sequences...............................................8 Lists & Tuples.............................................8 Operations on Sequences..........................8 Indexing.....................................................8 Operations on mutable sequences............ 8 Overriding Sequences Operations............. 8 Mappings (dictionaries)...........................8 Operations on Mappings............................8 Overriding Mapping Operations.................8 Other Mappings......................................... 8 Sets......................................................... 8 Operations on Sets.................................... 8 Other Containers Structures, Algorithms 9 Array..........................................................9 Queue........................................................9 Priority Queues..........................................9 Sorted List..................................................9 Iteration Tools............................................9 Date & Time............................................ 9 Module time...............................................9 Module datetime........................................9 Module timeit.............................................9 Other Modules......................................... 10 Files.......................................................10 File Objects..............................................10 Low-level Files......................................... 10 Pipes........................................................10 In-memory Files.......................................10 Files Informations.................................... 10 Terminal Operations................................ 11 Temporary Files.......................................11 Path Manipulations.................................. 11 Directories............................................... 11 Special Files.............................................11 Copying, Moving, Removing.................... 11 Encoded Files...........................................11 Serialization.............................................12 Persistence.............................................. 12 Configuration Files...................................12 Exceptions.............................................12 Standard Exception Classes.....................12 Warnings..................................................12 Exceptions Processing............................. 12 Encoding - Decoding............................. 12 Threads & Synchronization................... 12 Threading Functions................................ 12 Threads....................................................13 Mutual Exclusion......................................13 Events......................................................13 Semaphores.............................................13 Condition Variables..................................13 Synchronized Queues..............................13 Process..................................................13 Current Process....................................... 13 Signal Handling........................................14 Simple External Process Control..............14 Advanced External Process Control.........14 XML Processing..................................... 15 SAX - Event-driven...................................15 DOM - In-memory Tree............................ 16 Databases............................................. 17 Generic access to DBM-style DBs............17 Standard DB API for SQL databases........ 17 Bulk....................................................... 17 Styles : keyword function/method type replaced_expression variable literal module module_filename language_syntax Notations : f(…)→ return value f(…)➤ return nothing (procedure) [x] for a list of x data, (x) for a tuple of x data, may have x{n}→ n times x data. ENVIRONMENT VARIABLES PYTHONCASEOK 1 no case distinction in module→file mapping PYTHONDEBUG 1 = -d command-line option PYTHONHOME Modify standard Python libs prefix and exec prefix locations. Use [:]. PYTHONINSPECT 1 = -i command-line option PYTHONOPTIMIZE 1 = -O command-line option PYTHONPATH Directories where Python search when importing modules/packages. Separator : (posix) or ; (windows). Under windows use registry HKLM\Sofware\…. PYTHONSTARTUP File to load at begining of interactive sessions. PYTHONUNBUFFERED 1 = -u command-line option PYTHONVERBOSE 1 = -v command-line option 1 If set to non-empty value. COMMAND-LINE OPTIONS python [-dEhiOQStuUvVWx] [-c cmd | -m mod | file | -] [args] -d Output debugging infos from parser. -E Ignore environment variables. -h Print help and exit. -i Force interactive mode with prompt (even after script execution). -O Optimize generated bytecode, remove assert checks. -OO As -O and remove documentation strings. -Q arg Division option, arg in [old(default),warn,warnall,new]. -S Don't import definitions module. -t Warn inconsistent tab/space usage (-tt exit with error). -u Use unbuffered binary output for stdout and stderr. -U Force use of unicode literals for strings. -v Trace imports. -V Print version number and exit. -W arg Emit warning for arg "action:message:category:module:lineno" -x Skip first line of source (fort non-Unix forms of #!cmd). -c cmd Execute cmd. -m mod Search module mod in sys.path and runs it as main script. file Python script file to execute. args Command-line arguments for cmd/file, available in sys.argv[1:]. FILES EXTENSIONS .py=source, .pyc=bytecode, .pyo=bytecode optimized, .pyd=binary module, .dll/.so=dynamic library. .pyw=source associated to pythonw.exe on Windows platform, to run without opening a console. LANGUAGE KEYWORDS List of keywords in standard module keyword. and as1 assert break class continue def del elif else except exec finally for from global if import in is lambda not or pass print raise return try while yield 1 not reserved, but avoid to redefine it. Don't redefine these constants : None, True, False. BUILTINS Available directly everywhere with no specific import. Defined also in module __builtins__. Types basestring1 bool buffer complex dict exception file float frozenset int list long object set slice str tuple type unicode xrange 1 basestring is virtual superclass of str and unicode. This doc uses string when unicode and str can apply. Functions Constructor functions of builtin types are directly accessible in builtins. __import__ abs apply1 callable chr classmethod cmp coerce compile delattr dir divmod enumerate eval execfile filter getattr globals hasattr hash help hex id input intern2 isinstance issubclass iter len locals map max min oct open ord pow property range raw_input reduce reload repr reversed round setattr sorted staticmethod sum super unichr vars zip 1 Use f(*args,**kargs) in place of apply(f,args,kargs). 2 Don't use intern. STATEMENTS One statement per line1. Can continue on next line if an expression or a string is not finished ( ( [ { """ ''' not closed), or with a \ at end of line. Char # start comments up to end of line. pass Null statement. assert expr[,message] Assertion check expression true. del name[,…] Remove name → object binding. print [>>obj,][expr[,…][,] Write expr to sys.stdout2. exec expr [in globals [, locals]] Execute expr in namespaces. fct([expr[,…]],[name = expr [,…]] [,*args][,**kwargs]) Call any callable object fct with given arguments (see Functions Definitions & Usage - p2). name[,…] = expr Assignment operator3. 1 Multiple statements on same line using ; separator - avoid if not necessary. 2 Write to any specified object following file interface (write method). Write space between expressions, line-return at end of line except with a final ,. 3 Left part name can be container expression. If expr is a sequence of multiple values, can unpack into multiple names. Can have multiple assignments of same value on same line : a = b = c = expr. Other statements (loops, conditions…) introduced in respective parts. Blocks A : between statements defines dependant statements, written on same line or written on following line(s) with deeper indentation. Blocks of statements are simply lines at same indentation level. if x<=0 : return 1 if asin(v)>pi/4 : a = pi/2 b = -pi/2 else : a = asin(v) b = pi/2-a Statement continuation lines don't care indentation. To avoid problems, configure your editor to use 4 spaces in place of tabs. Assignment Shortcuts a += b a -= b a *= b a /= b a //= b a %= b a **= b a &= b a |= b a ^= b a >>= b a <<= b Evaluate a once, and assign to a the result of operator before = applied to current a and b. Example : a%=b ≈ a=a%b CONSOLE & INTERACTIVE INPUT/OUTPUT print expression[,…] 1a 1b 1c input([prompt]) → evaluation of user input (typed data) raw_input([prompt]) → str: user input as a raw string Direct manipulation (redefinition) of stdin/stdout/stderr via sys module : sys.stdin sys.stdout sys.stderr sys.__stdin__ sys.__stdout__ sys.__stderr__ All are files or files-like objects. The __xxx__ forms keep access to original standard IO streams. Ctrl-C raises KeyboardInterrupt exception. _ → value of last expression evaluation help([object]) ➤ print online documentation sys.displayhook → (rw) fct(value) called to display value sys.__displayhook__ → backup of original displayhook function sys.ps1 → str: primary interpreter prompt sys.ps2 → str: secondary (continuation) interpreter prompt See external package ipython for an enhanced interactive Python shell. OBJECTS, NAMES AND NAMESPACES Identifiers Use : [a-zA-Z_][a-zA-Z0-9_]* Special usage for underscore : _xxx global not imported by import * _xxx implementation detail, for internal use (good practice) __xxx 'private' class members, defined as _ClassName__xxx __xxx__ normally reserved by Python Case is significant : This_Name != THIS_NAME. Objects and Names, Reference Counting Data are typed objects (all data), names are dynamically bound to objects. = assignment statement bind result of right part evaluation into left part name(s)/container(s). Examples : a = 3*c+5 s = "Hello" a,b = ("Hello","World") pi,e = 3.14,2.71 x,y,tabz[i] = fct(i) a,b = b,a When an object is no longer referenced (by names or by containers), it is destroyed (its __del__ method is then called). sys.getrefcount(object)→ int: current reference counter of object Standard module weakref define tools to allow objects to be garbage collected when necessary and dynamically re-created on-demand. Mutable/Immutable Objects Mutable objects can be modified in place. Immutable objects cannot be modified (must build a new object with new value). Immutable : bool, int, long, float, complex, string, unicode, tuple, frozenset, buffer, slice. Mutable : list, set, dict and other high level class objects. There is no constant definition. Just use uppercase names to identify symbols which must not be modified. Namespaces Places where Python found names. Builtins namespace → names from module __builtins__, already available. Global namespace → names defined at module level (zero indentation). Local namespace → names defined in methods/functions. del name ➤ remove existing name from namespace (remove object binding) globals() → dict: identifier→value of global namespace locals() → dict: identifier→value of local namespace Current scope → names directly usable. Searched in locals, then locals from enclosing definitions, then globals, then builtins. Out-of-scope name → use the dotted attribute notation x.y (maybe x.y.z.t)… where x is a name visible within the current scope. Class namespace → names defined in a class (class members). Object namespace → names usable with notation (attributes, methods). Namespaces can be nested, inner namespaces hidding identical names from outer namespaces. dir([object]) → list: names defined in object namespace1 vars([object]) → dict2: identifier:value of object as a namespace1 1 if object not specified use nearest namespace (locals). 2 must not be modified. Constants, Enumerations Use uppercase and _ for constants identifiers (good practice). May define namespaces to group constants. Cannot avoid global/local name redefinition (can eventually define namespaces as classes with attributes access control - not in Python spirit, and execution cost). See third party modules pyenum for strict enum-like namespace. FLOW CONTROL Condition if cond : inst [ elif cond : inst ] [ else : inst ] There is no 'switch' or 'case'. Can use if elif elif… else. Can use a mapping with functions bound to cases. Loop for var[,…] in iterable : inst [ else : inst ] while cond : inst [ else : inst ] Exit loop with break. Go to next iteration with continue. Loops else blocs only executed when loop exit normally (without break). Functions/methods exit Exit function/method with return [value] Exit from generator body with yield value Multiple returned values using tuple data. Cannot yield within a try/finally block. Exceptions try : inst except [ except_class [ , value ]] : inst … [ else : inst ] Can have a tuple of classes for except_class. Not specifying a class catch all exceptions. Block else executed when try block exit normally. try : inst finally : inst Process finally block in all execution paths (normal or exception). raise exception_class[,value[,traceback]] raise exception_object raise Last form re-raise the currently catched exception in an exception handler. Iterable Protocol Generic and simple protocol allowing to iterate on any collection of data. Objects of class defining __iter__ or __getitem__ are iterable (directly usable in for loops). __iter__(self) → iterator on self iter(object) → iterator on iterable object iter(callable,sentinel) → iterator returning callable() values up to sentinel enumerate(iterable)→ iterator returning tuples (index,value) from iterable Iterators Objects Interface next(self)→ next item1 __iter__(self)→ iterator object itself 1 When reach end of collection, raise StopIteration exception on subsequent calls (ie. iterator usable only one time on a collection). Generators Functions retaining their state between two calls. Return values using yield. Stop generation via simple return or via raise StopIteration. 1) build generator from function : gen=generatorfct(args) 2) use values until StopIteration is raised. Generator iterable expressions with : (x for x in iterable where cond) Operations with/on Iterable See Operations on Containers (p7). See Iteration Tools (p9). INTERPRETATION / EXECUTION compile(string1,filename,kind2[,flags3[,dont_inherit3]]) → code object eval(expression[,globals[,locals]]) → value: evaluation4 of expression string eval(code_object[,globals[,locals]]) → value: evaluation4 of code_object exec5 statements [in globals[,locals]] ➤ statements string1 executed4 execfile(filename[,globals[,locals]]) ➤ file filename interpreted4 1 Multi-line statements in source code must use \n as newline, and must be terminated by a newline. 2 Kind relative to string content, 'exec' → sequence of statements, 'eval' → single expression, 'single' → single interactive statement. 3 Flags and dont_inherit are for future statements (see doc). 4 In context of globals and locals namespaces. 5 Exec is a langage statement, others are builtin functions. FUNCTIONS DEFINITIONS & USAGE def fctname([paramname [ = defaultvalue ] [,…]] [,*args][,**kwargs]) : instructions new.function(code,globals[,name[,argdefs]]) → python function (see docs) Parameters / Return value Parameters are passed by references to objects. You can modify values of mutable objects types. You cannot modify values of immutable objects types - as if they were passed by value. Notation * → variable list of anonymous parameters in a tuple. Notation ** → variable list of named parameters in a dict. Return value(s) with return [value[,…]] For multiple values, return a tuple. If no return value specified or if end of function definition reached, return None value. Lambda functions lambda param[,…] : expression Anonymous functions defined inline. Result of expression evaluation is returned (it must be an expression, no loop, no condition). Expression uses values known at definition time (except for params). Callable Objects Objects having a __call__ method can be used as functions. Methods bound to objects can be used as functions : f = o.meth callable(x) → bool: test x callable with x(…) Calling Functions [name=] fctname([expr[,…]][,name=expr[,…][,*args][,**args]) Anonymous parameters passed in parameters order declaration. Params having default value can be omitted. Notation * → pass variable list of anonymous parameters in a tuple. Notation ** → pass variable list of named parameters in a dict. Functions Control sys.getrecursionlimit()→ int: current recursion limit for functions sys.setrecursionlimit(limit) ➤ set recursion limit for functions Decorators Glue code (functions) called at functions and methods definitions time, return the final function/method (generally with wrapping code). 2a 2b 2c @ decoratorname [ ( decorator_arguments ) ] […] def fct(fct_rguments):… @dec1 @dec2(args) @dec3 def fct(…):… like ➤ def fct(…):… fct = dec1(dec2(args)(dec3(fct)))) See page PythonDecoratorLibrary in Wiki for some decorators definitions. TYPES/CLASSES & OBJECTS All data are typed objects relying to classes. type(o) → type: type object of o Standard module types define type objects for builtins types. Class Definition class classname [(parentclass[,…])] : varname = expr ➤ varname defined in classname namespace def metname(self[,…]): ➤ define methods like functions Support multiple inheritance. Can inherit from builtin class. Inherit at least from object base class => Python 'new style class'. First parameter of methods is target object, standard use self name. Access class members via class name, object members via self. This doc consider you use new style class (inheriting from object). new.classobj(name,baseclasses,dict) → new class (see docs) new.instancemethod(fct,instance,class) → new method: bound to instance it it is not None, see docs Metaclass Class definition create a new type. It can be done 'by hand' with : x = type('classname',(parentclass , […]),{varname:expr[,…]} def metname(self[,…]): x.metname = metname This allow creation of metaclass class (class building other class). Object Creation obj = ClassName(initargs…) In case of exception during initialization, object is destroyed when exiting init code (reference counter reach zero). new.instance(class[,dict]) → object: create new class instance without calling __init__ method, dict is initial object attributes Classes & Objects Relations isinstance(obj,classinfo) → bool: test object kind of type/class classinfo issubclass(aclass,aparent) → bool: test same class or parent relationship Prefer isinstance() to type() for type checking. Parent class methods are not automatically called if overriden in subclass - they must be explicitly called if necessary. Call parent methods via super function : super(ThisClass,self).methodname(self,args…) Or the old way, via parent class namespace : ParentClass.methodname(self,args…) Attributes Manipulation = value setattr(object,name,value) ➤ object attribute set to value → value of object attribute getattr(object,name[,default])→ value of object attribute del delattr(object,name) ➤ object attribute removed Special Methods Other special overridable __xxx___ methods are listed in respective sections. Object Life __new__(classref,initargs…)→ object of classref type, already initialized1 __init__ (self,initargs…)➤ called to initialize object with initargs __del__ (self)➤ called when object will be destroyed 1 If don't return a classref object, then object.__init__ is called with initargs. Object Cast __repr__(self)→ str: called for repr(self) and `self` __str__(self) → str: called for str(self) and print self __coerce__(self,other) → value, called for coerce(self,other) Object Hash Key __hash__(self)→ int: 32 bits hash code for object, used for hash(obj)and quick dict mapping keys comparison - default implementation use hash(id(self)) Attributes access See also "Descriptors protocol" infra. __getattr__(self,name)→ value, called for undefined attributes __getattribute__(self, name)→ value, always called __setattr__(self, name, value) ➤ called for __delattr__(self, name) ➤ called for del __call__(self, *args, **kwargs)→ value, called for obj(…) Static method / Class method Use standard decorators (see Decorators p2). class ClassName : @staticmethod def methodname(…): … @classmethod def methodname(classref,…): … Descriptors protocol Descriptors are attribute objects controling access to attributes values. They must define some of following methods : __get__(self,obj,ownerclass)→ attribute value for obj __set__(self,obj,value) ➤ modify attribute in obj, set to value __delete__(self,obj) ➤ remove attribute from obj In these methods self is the descriptor object, and obj is the target object which attribute is manipulated. Properties A descriptor to directly bind methods/functions to control attribute access. Use builtin type property with init args. class MyClass : attributename = property(getter,setter,deleter,description) Each init arg default to None (ie. undefined). Copying Objects Assignment only duplicate references. To shallow copy an object (build a new one with same values - referencing same content), or to deep copy an object (deep-copying referenced content), see object copy methods, and functions in standard module copy. copy.copy(object)→ value: shallow copy of object copy.deepcopy(object[[,memo],_nil])→ value: deep copy of object1 1 Params memo and nil are used in recursive deepcopy, their default values are None and empty list. Copy Protocol __copy__(self)→ value: shallow copy of self, called by copy.copy(…) __deepcopy__(self,memo)→ value: deep copy of self, called by copy.deepcopy(…) For copying, objects can define pickling protocol too (see Files - Serialization - p12), in place of __copy__ and __deepcopy__. Introspection Beyond this documentation. Many __xxx___ attributes are defined, some are writable (see other docs). See standard module inspect to manipulate these data. Example of Introspection Attributes Note: classes are objects too! __base__ → list: parent classes of a class __slots__ → tuple: allowed objects attributes names1 of a class __class__ → class/type: object's class __dict__ → dict: defined attributes (object namespace) of an instance __doc__ → string: documentation string of a package, module, class, function __name__ → str: object definition name of a function __file__ → string: pathname of loaded module .pyc, .pyo or .pyd 1 List of allowed attributes names. Usage discouraged. MODULES AND PACKAGES File ➤ module gabuzo. Directory kramed/ with a file ➤ package kramed. Can have sub-packages (subdirectories having file). Searched in the Python PATH. Current Python PATH stored in sys.path list. Contains directories and .zip files paths. Built from location of standard Python modules, PYTHONPATH environment variable, directory of main module given on command line, data specified in lines of .pth files found in Python home directory, and data specified in registry under Windows. Current list of loaded modules stored in sys.modules map (main module is under key __main__). import module [ as alias ] [,…] from module import name [ as alias ] [,…] from module import * reload(module) ➤ module is reloaded (but existing references still refer old module content) new.module(name[,doc]) → new module object. Import can use package path (ex:from encoding.aliases import…). Direct import from a package use definitions from file. Very careful with import * as imported names override names already defined. To limit your modules names exported and visible by import *, define module global __all__ with list of exported names (or use global names _xxx). See __import__ builtin function, and modules imp, ihooks. __import__(modulename[, globals[,locals[,lnameslist]]]) Source encodings See PEP 263. Declare source files encoding in first or second line in a special comment. # -*- coding: encoding_name -*- If this is not specified, Python use sys.getdefaultencoding() value (see modules and It is important to specify encoding of your modules as u"…" strings use it to correctly build unicode literals. Special Attributes __name__ → str: module name, '__main__' for command-line called script __file__ → string: pathname of compiled module loaded MAIN EXECUTION / SCRIPT PARAMETERS The 'main' module is the module called via command-line (or executed by shell with first script line #! /bin/env python). Command-line parameters are available in sys.argv (a python list). At end of module, we may have : if __name__=='__main__' : # main code # generally call a 'main' function: mainfunction(sys.argv[1:]) # or in lib modules, execute test/demo code... Execution exit after last main module instruction (in multithread, wait also for end of non-daemon threads), unless interactive mode is forced. 3a 3b 3c Can force exit with calling sys.exit(code), which raise a SystemExit exception - see Current Process - Exiting (p13). OPERATORS Deal with arithmetic, boolean logic, bit level, indexing and slicing. Priority 1 ( a , … ) [ a , … ] { a : b , … } ` … ` 6 x + y x - y 11 x < y x <= y x > y x >= y x == y x != y x <> y x is y x is not y x in s x not in s 2 s [ i ] s [ i : j ] s . attr f ( … ) 7 x<> y 12 not x 3 + x - x ~ x 8 x & y 13 x and y 4 x ** y 9 x ^ y 14 x or y 5 x * y x / y x % y 10 x | y 15 lambda args : expr Arithmetic Operators Can be defined for any data type. Arithmetic Overriding __add__(self,other) → value: called for self + other __sub__(self,other) → value: called for self - other __mul__(self,other) → value: called for self * other __div__(self,other) → value: called1 for self / other __truediv__(self,other) → value: called2 for self / other __floordiv__(self,other) → value: called for self // other __mod__(self,other) → value: called for self % other __divmod__(self,other) → value: called for divmod(self,other) __pow__(self,other) → value: called for self ** other __nonzero__(self)→ value: called for nonzero(self) __neg__(self) → value: called for -self __pos__(self) → value: called for +self __abs__(self) → value: called for abs(self) __iadd__(self,other) ➤ called for self += other __isub__(self,other) ➤ called for self -= other __imul__(self,other) ➤ called for self *= other __idiv__(self,other) ➤ called1 for self /= other __itruediv__(self,other) ➤ called2 for self /= other __ifloordiv__(self, other) ➤ called for self //= other __imod__(self,other) ➤ called for self %= other __ipow__(self,other) ➤ called for self **= other 1 without / 2 with from __futur__ import division Binary operators __xxx__ have also __rxxx__ forms, called when target object is on right side. Comparison Operators Operators can compare any data types. Compare values with < <= > >= == != <>. Test objects identity with is and is not (compare on id(obj)). Direct composition of comparators is allowed in expressions : xt. Builtin function cmp(o1,o2) → -1 (o1 < o2), 0 (o1 == o2), 1 (o1 > o2) Comparison Overriding __lt__(self, other)→ bool1: called for self < other __le__(self, other)→ bool1: called for self <= other __gt__(self, other)→ bool1: called for self > other __ge__(self, other)→ bool1: called for self >= other __eq__(self, other)→ bool1: called for self == other __ne__(self, other)→ bool1: called for self != other and for self <> other __cmp__(self,other)→ int: called for self compared to other, selfother→value>0 1 Any value usable as boolean value, or a NotImplemented value if cannot compare with such other type. Operators as Functions Operators are also defined as functions in standard operator module. Comparison lt(a,b) = __lt__(a,b) le(a,b) = __le__(a,b) eq(a,b) = __eq__(a,b) ne(a,b) = __ne__(a,b) ge(a,b) = __ge__(a,b) gt(a,b) = __gt__(a,b) Logical / Boolean not_(o) = __not__(o) truth(o) is_(a,b) is_not(a,b) and_(a,b) = __and__(a,b) or_(a,b) = __or__(a,b) xor(a,b) = __xor__(a,b) Arithmetic abs(o) = __abs__(o) add(a,b) = __add__(a,b) sub(a,b) = __sub__(a,b) mul(a,b) = __mul__(a,b) div(a,b) = __div__(a,b) mod(a,b) = __mod__(a,b) truediv(a,b) = __truediv__(a,b) floordiv(a,b) = __floordiv__(a,b) neg(o) = __neg__(o) pos(o) = __pos__(o) pow(a,b) = __pow__(a,b) Bit Level lshift(a,b) = __lshift__(a,b) rshift(a,b) = __rshift__(a,b) inv(o) = invert(o) = __inv__(o) = __invert__(o) Sequences concat(a,b) = __concat__(a,b) contains(a,b) = __contains__(a,b) countOf(a,b) indexOf(a,b) repeat(a,b) = __repeat__(a,b) setitem(a,b,c) = __setitem__(a,b,c) getitem(a,b) = __getitem__(a,b) delitem(a,b) = __delitem__(a,b) setslice(a,b,c,v) = __setslice__(a,b,c,v) getslice(a,b,c) = __getslice__(a,b,c) delslice(a,b,c) = __delslice__(a,b,c) Type Testing These functions must be considered as not reliable. isMappingType(o) isNumberType(o) isSequenceType(o) Attribute and Item Lookup attrgetter(attr) → fct: where fct(x)→x.attr itemgetter(item) → fct: where fct(x)→x[item] BOOLEANS False : None, zero numbers, empty containers. False → 0. True : if not false. True → 1. bool(expr) → True | False Logical not : not expr Logical and : expr1 and expr2 Logical or : expr1 or expr2 Logical and and or use short path evaluation. Bool Cast Overriding __nonzero__(self) → bool: test object itself1 1 If __nonzero__ undefined, look at __len__, else object is true. NUMBERS Builtin integer types : int (like C long), long (unlimited integer) int(expr[,base=10]) → int: cast of expr long(expr[,base=10]) → long: cast of expr Builtin floating point types : float (like C double), complex (real and imaginary parts are float). float(expr) → float: representation of expr complex(x[,y]) → complex: number: x+yj [x+]yj → complex: number, ex: 3+4j -8.2j c.real → float: real part of complex number c.img → float: imaginary part of complex number c.conjugate() → complex: conjugate of complex number (real,-img) Maximum int integer in sys.maxint. Automatic conversions between numeric types. Automatic conversions from int to long when result overflow max int. Direct conversions from/to strings from/to int, long… via types constructors. Type Decimal defined in standard module decimal. Base fixed type compact storage arrays in standard module array. Operators -x +x x+y x-y x*y x/y 1 x//y 1 x%y 2 x**y 2 1 With from __future__ import division, / is true division (1/2→0.5), and // is floor division (1//2→0). Else for integers / is still floor division. 2 % is remainder operator, ** is power elevation operator (same as pow). Functions Some functions in builtins. abs(x) → absolute value of x divmod(x,y) → (x/y,x%y) oct(integer) → str: octal representation of integer number hex(integer) → str: hexadecimal representation of integer number Representation formating functions in strings Formating (p5) and Localization (p6). Math Functions Standard floating point functions/data in standard math module. acos(x) → float: radians angle for x cosinus value : [-1…1] →[0…π] asin(x) → float: radians angle for x sinus value : [-1…1] →[-π/2…+π/2] atan(x) → float: radians angle for x tangent value : [-∞…∞] →]-π/2…+π/2[ atan2(x,y) → float: randians angle for x/y tangent value ceil(x) → float: smallest integral value >= x cos(x) → float: cosinus value for radians angle x cosh(x) → float: hyperbolic cosinus value for radians angle x exp(x) → float: exponential of x = ex fabs(x) → float: absolute value of x floor(x) → float: largest integral value <= x fmod(x,y) → float: modulo = remainder of x/y frexp(x) → (float,int): (m,y) m mantissa of x, y exponent of x — where x=m*2y ldepx(x,i) → float: x multiplied by 2 raised to i power: x * 2i log(x) → float: neperian logarithm of x log10(x) → float: decimal logarithm of x modf(x) → (float{2}): (f,i) f signed fractional part of x, i signed integer part of x pow(x,y) → float: x raised to y power (xy) sin(x) → float: sinus value for radians angle x sinh(x) → float: hyperbolic sinus value for radians angle x sqrt(x) → float: square root of x (√x) tan(x) → float: tangent value for radians angle x tanh(x) → float: hyperbolic tangent value for radians angle x pi → float: value of π (pi=3.1415926535897931) e → float: value of neperian logarithms base (e=2.7182818284590451) Module cmath provides similar functions for complex numbers. Random Numbers Randomization functions in standard random module. Module functions 4a 4b 4c use an hidden, shared state, Random type generator (uniform distribution). Functions also available as methods of Random objects. seed([x]) ➤ initialize random number generator random()→ float: random value in [0.0, 1.0[ randint(a,b)→ int: random value in [a, b] uniform(a, b)→ float: random value in [a, b[ getrandbits(k)→ long: with k random bits randrange([start,]stop[,step])→ int: random value in range(start, stop, step) choice(seq)→ value: random item from seq sequence shuffle(x[,rndfct]) ➤ items of x randomly reordered using rndfct() sample(population,k)→ list: k random items from polulation Alternate random distributions : betavariate(alpha,beta), expovariate(lambd), gammavariate(alpha,beta), gauss(mu,sigma), lognormvariate(mu, sigma), normalvariate(mu,sigma), vonmisesvariate(mu,kappa), paretovariate(alpha), weibullvariate(alpha,beta). Alternate random generator WichmannHill class. Direct generator manipulation : getstate(), setstate(state), jumpahead(n). In module os, see : os.urandom(n) → str: n random bytes suitable for cryptographic use Other Math Modules Advanced matrix, algorithms and number crunching in third party modules like numpy (evolution of numarray / Numeric), gmpy (multiprecision arithmetic), DecInt, scipy, pyarray, … See sites SciPy, BioPython, PyScience,… Numbers Casts Overriding __int__(self) → int: called for int(self) __long__(self) → long: called for long(self) __float__(self) → float: called for float(self) __complex__(self) → complex: called for complex(self) __oct__(self) → str: called for oct(self) __hex__(self) → str: called for hex(self) __coerce__(self,other) → value: called for coerce(self,other) BIT LEVEL OPERATIONS Work with int and long data. Operators ~x → inverted bits of x x^y → bitwise exclusive or on x and y x&y → bitwise and on x and y x|y → bitwise or on x and y x<>n → x shifted right by n bits (zeroes inserted) Binary structures manipulations in standard module struct. Advanced binary structures mapping and manipulation in third party modules : ctypes, xstruct, pyconstruct, … Bit Level Overriding __and__(self,other) → value: for self & other __or__(self,other) → value: for self | other __xor__(self,other) → value: for self ^ other __lshift__(self,other) → value: for self << other __rshift__(self,other) → value: for self >> other __invert__(self) → value: for ~self __iand__(self,other) ➤ called for self &= other __ior__(self,other) ➤ called for self |= other __ixor__(self,other) ➤ called for self ^= other __ilshift__(self,other) ➤ called for self <<= other __irshift__(self,other) ➤ called for self >>= other STRINGS Simple quoted 'Hello' or double-quoted "Hello". Use triple [simple|double] quotes for multi-lines strings : """Hello, how are you ?""" Strings are immutable (once created a string cannot be modified in place). Strings can contain binary data, including null chars (chars of code 0). Strings are sequences, see Indexing (p8) for chars indexation (slicing) and other operations. chr(code)→ str: string of one char ord(char)→ int: code str(expr)→ str: readable textual representation of expr - if available `expr` → str: readable textual representation of expr - if available repr(expr)→ str: evaluable textual representation of expr - if available Escape sequences \a - bell \b - backspace \e - escape \f - form feed \n - new line \r - carriage return \t - horizontal tab \v - vertical tab \' - single quote \" - double quote \\ - backslash \ooo - char by octal ooo value \xhh - char by hexadecimal hh value \ - continue string on next line. And for Unicode strings : \uxxxx - unicode char by 16 bits hexadecimal xxxx value. \Uxxxxxxxx - unicode char by 32 bits hexadecimal xxxxxxxx value. \N{name} - unicode char by name in the Unicode database. Keep \ escape chars by prefixing string literals with a r (or R) - for 'raw' strings (note : cannot terminate a raw string with a \). Unicode strings Quoted as for str, but with a u (or U) prefix before the string : u"Voiçi" U"""Une bonne journée en perspective.""" Can mix strings prefixs r (or R) and u (or U). You must define your source file encoding so that Python knows how to convert your source literal strings into internal unicode strings. unichr(code) → unicode: string of one char ord(unicode char) → int: unicode code unicode(object[,encoding[,errors]]) → unicode: unicode sys.maxunicode → int: maximum unicode code=fct(compile time option) Unicode Chars Informations Module unicodedata contains informations about Unicode chars properties, names. lookup(name) → unicode: unicode char from its name name(unichr[,default]) → str: unicode name - may raise ValueError decimal(unichr[,default]) → int: decimal value - may raise ValueError digit(unichr[,default]) → int: digit value - may raise ValueError numeric(unichr[,default]) → float: numeric value - may raise ValueError category(unichr) → str: general unicode category of char bidirectional(unichr) → str: bidir category of char, may be empty string combining(unichr) → str/0: canonical combining class of char as integer east_asian_width(unichr) → str: east asian width mirrored(unichr) → int: mirrored property in bidi text, 1 if mirrored else 0 decomposition(unichr) → str: decomposition mapping, may be empty str normalize(form, unistr) → str: normal form of string - form in 'NFC', 'NFKC', 'NFD', 'NFKD' unidata_version → str: version of Unicode database used Methods and Functions From builtins (see also oct and hex functions for integers to strings) : len(s) → int: number of chars in the string Most string methods are also available as functions in the standard string module. s.capitalize() → string with first char capitalized1[,fillchar]) → string centered s.count(sub[,start[,end]]) → int: count sub occurences s.decode([encoding[,errors]]) → unicode: text decoded - see encodings (p12) s.encode([encoding[,errors]]) → str: text encoded - see encodings (p12) s.endswith(suffix[,start[,end]]) → bool: test text ending s.expandtabs([tabsize]) → string with tabs replaced by spaces s.find(sub[,start[,end]]) → int/-1: offset of sub s.index(sub[,start[,end]]) → int: offset of sub - may raise ValueError s.isalnum() → bool: non empty string with all alphanumeric chars1 s.isalpha() → bool: non empty string with all alphabetic chars1 s.isdigit() → bool: non empty string with all digit chars1 s.islower() → bool: non empty string with all lower chars1 s.isspace() → bool: non empty string with all space chars1 s.istitle() → bool: non empty string with titlecase words1 s.isupper() → bool: non empty string with all upper chars1 s.join(seq) → string: seq[0]+s+seq[1]+s+…+seq[n-1] s.ljust(width[,fillchar]) → text string left aligned2 s.lower() → text string lowered1 s.lstrip([chars]) → string text with leading chars2 removed s.replace(old,new[,count]) → string with count firsts old replaced by new s.rfind(sub[,start[,end]]) → int/-1: last offset of sub s.rindex(sub[,start[end]])→ int: last offset of sub - may raise ValueError s.rjust(width[,fillchar]) → string text right aligned2 s.rsplit([sep[,maxsplit]])→ [string]: rightmost words delim. by sep2 s.rstrip([chars]) → string with trailing chars2 removed s.split([sep[,maxsplit]]) → [string]: words delimited by sep2 s.splitlines([keepends]) → [string]: list of text lines s.startswith(suffix[,start[,end]]) → bool: test text begining s.strip([chars]) → string text with leading+trailing chars2 removed s.swapcase() → string with case switched1 s.title() → string with words capitalized1 s.translate(table[,deletechars]) → string: cleaned, converted3 s.upper() → string uppered1 s.zfill(witdh) → string: string prefixed with zeroes to match width 1 Locale dependant for 8 bits strings. 2 Default chars/separator/fillchar is space. 3 For str table must be a string of 256 chars - see string.maketrans(). For Unicode no deletechars, and table must be a map of unicode ordinals to unicode ordinals. Formating Use % operator between format string and arguments : string%args Formating string contains %[(name)][flag][width][.precision]code If not use %(name)… → args = single value or tuple of values. If use %(name)… → args = mapping with name as keys. For mapping, args can be an object with __getitem__ method - see Overriding Mapping Operations (p8). Format char codes d signed int. decimal : -324 i signed int. decimal : -324 o unsigned octal : 774 u unsigned decimal 6953 x unsigned hexa : f3a X unsigned hexa : F3A e float. point exp. : -3.256e-12 E float. point exp. : -3.256E-12 f float. point dec. : -0.0000032 F float. point dec. : -0.0000032 g like e or f G like E or F c character (1 char str or code) % %% → % r object format like repr(object) s object format like str(object) Templates With string.Template objects. Use common $ syntax : $$ ➤ single $ ; $name or ${name} ➤ value for name. 5a 5b 5c tmpl = string.Template(template_string) tmpl.substitute(mapping[,**kwargs]) → string: template filled tmpl.safe_substitute(mapping[,**kwargs]) → string: template filled tmpl.template → string Can subclass Template to build your own templating (see doc, sources). See also modules formatter. Wrapping Module textwrap has a TextWrapper class and tool functions. tw = textwrap.TextWrapper([…]) → new text wrapper using named params as corresponding attributes values tw.width → int: max length of wrapped lines (default 70) tw.expand_tabs → bool: replace tabs by text.expandtabs() (default True) tw.replace_whitespace → bool: replace each whitespace by space (default True) tw.initial_indent → string: prepend to first wrapped line (default '') tw.subsequent_indent → string: prepend to other wrapped lines (default '') tw.fix_sentence_endings → bool: try to separate sentences by two spaces (default False) tw.break_long_words → bool: break words longer than width (default True) tw.initial_indent → string: prepend to first wrapped line (default '') tw.wrap(text) → [string]: list of text lines, each with max width length - no final newline tw.fill(text) → string: whole text, lines wrapped using newlines Two convenient functions use temporary TextWrapper, built using named parameters corresponding to attributes. wrap(text[,width=70[,…]]) → [string] fill(text[,width=70[,…]]) → string dedent(text) → string: remove uniform whitespaces at beginning of text lines Constants Standard module string provide several constants (do not modify, they are used in string manipulation functions) and some str functions are not available as methods. ascii_letters → str: lowercase and uppercase chars ascii_lowercase → str: lowercase a-z chars ascii_uppercase → str: uppercase A-Z chars digits → str: 0-9 decimal digit chars hexdigits → str: 0-9a-fA-F hexadecimal digit chars letters → str: lowercase and uppercase chars1 lowercase → str: lowercase a-z chars1 octdigits → str: 0-7 octal digit chars punctuation → str: ascii chars considered as punctuation in C locale printable → str: printable chars uppercase → str: uppercase A-Z chars1 whitespace → str: whitespace chars (spc, tab, cr, lf, ff, vt) capwords(s) → str: split → capitalize → join maketrans(from,to) → translation table usable in str.translate - from and to must have same length 1 Definition is locale dependant. Regular Expressions Standard module re has a powerfull regexp engine. See regexp HOWTO at Use raw string r"…" notation. See also external projects pyparsing, PLY (Python Lex-Yacc), tpg (Toy Parser Generator)… Expressions Metacharacters : . ^ $ * + ? { } [ ] \ | ( ), may use \ escape. . ➤ match any character except a newline (including newline with DOTALL option) ^ ➤ match start of string (and start of lines with MULTILINE option) $ ➤ match end of string (and end of lines with MULTILINE option) expr* ➤ match 0 or more repetitions of expr (as much as possible) expr+ ➤ match 1 or more repetitions of expr (as much as possible) expr? ➤ match 0 or 1 expr expr*? ➤ match like expr* but as few as possible expr+? ➤ match like expr+ but as few as possible expr?? ➤ match like expr? but as few as possible expr{m} ➤ match m repetitions of expr expr{[m],[n]} ➤ match from m to n repetitions of expr, missing m default to 0 and missing n default to infinite expr{[m],[n]}? ➤ match like expr{[m],[n]} but as few as possible [set] ➤ match one char in the set defined by : ^ → at begining, invert set definition x-y → chars from x to y \x → see Escape sequences for strings (p5) \- , \] → chars - and ] (- and ] at the beginning match - and ] chars) x → char x (including other re metacharacters) exprA|exprB ➤ match exprA or exprB, short path evaluation (expr) ➤ match expr and build a numbered group (?[i][L][m][s][u][x]) ➤ (at least one ot iLmsux char) group match empty string, modify options flags for entire expression - see I L M S U X options (?:expr) ➤ match expr but dont build a group (?Pexpr) ➤ match expr and build a group numbered and named (name must be valid Python identifier) (?P=name) ➤ match text matched by earlier group named name (?#text) ➤ no match, text is just a comment (?=expr) ➤ match if match expr but don't consume input (?!expr) ➤ match if doesn't match expr but don't consume input (?<=expr) ➤ match if current position is immediatly preceded by a match for fixed length pattern expr (? and \g. 1 Using part of string between pos and endpos. Group number 0 correspond to entire matching. Localization Standard module locale provide posix locale service (internationa- lization). setlocale(category[,locale]) → current/new settings: if locale specified (as string or as tuple(language code, encoding)) then modify locale settings for 6a 6b 6c category and return new one - if locale not specified or None, return current locale - not thread safe localeconv()→ dict: database of local conventions nl_langinfo(option)→ string: locale-specific informations - not available on all systems - options may vary on systems - see options p7 getdefaultlocale([envvars])→(language code, encoding): try to determine default locale settings getlocale([category])→ current LC_* setting for category - category default to LC_CTYPE - for language code and ancoding it may be None getpreferredencoding([do_setlocale])→ str: user preffered encoding for text data - set do_setlocale to False to avoid possible call to setlocale() normalize(localename)→ normalized locale code for localename - usable with setlocale() - return localename if normalization fails resetlocale([category]) ➤ reset locale for category to default setting - category default to LC_ALL strcoll(s1,s2)→ int: compare two strings - follow LC_COLLATE setting - return 0 if s1==s2, <0 if s10 if s1>s2 strxfrm(string)→ string:transform string for locale-aware comparison format(format,val[,grouping])→ string:convert val float using format (% operator conventions) - follow LC_NUMERIC settings (decimal point, + grouping if it is true) str(float)→ string: convert float - follow LC_NUMERIC settings (decimal point) atof(string)→ float: convert string to float - follow LC_NUMERIC settings atoi(string)→ int: convert string to integer - follow LC_NUMERIC settings CHAR_MAX → symbolic constant used by localeconv() Categories LC_CTYPE → character type - case change behaviour LC_COLLATE → strings sorting - strcoll() and strxfrm() functions LC_TIME → time formating - time.strftime() LC_MONETARY → monetary values formating - options from localeconv() LC_MESSAGES → messages display - os.strerror() - not for Python messages LC_NUMERIC → numbers formatting - format(), atoi(), atof() and str() of this module (dont modify normal Python number formating) LC_ALL → all locales - used to change/retrieve the locale for all categories nl_langinfo options key nl_langinfo() value usage CODESET name of character encoding D_T_FMT usable as format for strftime() for time and date D_FMT usable as format for strftime() for date T_FMT usable as format for strftime() for time T_FMT_AMPM usable as format for strftime() for time in am/pm format DAY_1…DAY_7 name of the nth day of the week - first day is sunday ABDAY_1… ABDAY_7 abbreviated name of the nth day of the week - first day is sunday MON_1… MON_12 name of the nth month ABMON_1… ABMON_12 abbreviated name of the nth month RADIXCHAR radix character (decimal dot/comma/…) THOUSEP separator character for thousands YESEXPR regular expression (of C library!) usable for yes reply NOEXPR regular expression (of C library!) usable for no reply CRNCYSTR currency symbol, preceded by - if should appear before the value, by + if should appear after the value, by . if should replace radix character ERA era - generally not defined - same as E format in strftime() ERA_YEAR year in era ERA_D_T_FMT usable as format for strftime() for date and time with era key nl_langinfo() value usage ERA_D_FMT usable as format for strftime() for date with era ALT_DIGITS up to 100 values representing 0 to 99 localeconv keys key meaning currency_symbol Local currency symbol for monetary values. decimal_point Decimal point character for numbers. frac_digits Number of fractional digits used in local formatting of monetary values. grouping [int]: relative positions of 'thousands_sep' in numbers. CHAR_MAX at the end stop grouping. 0 at the end repeat last group. int_curr_symbol International currency symbol of monetary values. int_frac_digits Number of fractional digits used in international formatting of monetary values. mon_decimal_point Decimal point used for monetary values. mon_grouping Equivalent to 'grouping', used for monetary values. mon_thousands_sep Group separator used for monetary values. n_cs_precedes True if currency symbol preceed negative monetary values, false if it follow. n_sep_by_space True if there is a space between currency symbol and negative monetary value. n_sign_posn Position of negative sign for monetary values1. negative_sign Symbol used to annotate a negative monetary value. p_cs_precedes True if currency symbol preceed positive monetary values, false if it follow. p_sep_by_space True if there is a space between currency symbol and positive monetary value. p_sign_posn Position of positive sign for monetary values1. positive_sign Symbol used to annotate a positive monetary value. thousands_sep Character used between groups of digits in numbers. 1 Possible values : 0=currency and value surrounded by parentheses, 1=sign should precede value and currency symbol, 2=sign should follow value and currency symbol, 3=sign should immediately precede value, 4=sign should immediately follow value, LC_MAX=nothing specified in this locale. Multilingual Support Standard module gettext for internationalization (I18N) and localization (L10N) services - based on GNU gettext API + higher interface. See docs for explanations about tools usage. Base API bindtextdomain(domain[,localedir])→ str: bounded directory - bind domain to localedir directory if specified (used when searching for .mo files) bind_textdomain_codeset(domain[,codeset])→ codeset binding: bind domain to codeset if specified - change xxgettext() returned strings encoding textdomain([domain])→ global domain: set global domain if specified and not None gettext(message)→ string: localized translation of message - based on current global domain, language, and locale directory - usually aliased as _ in local namespace lgettext(message)→ string: like gettext(), using preferred encoding dgettext(domain,message)→ string: like gettext(), looking in specified domain. ldgettext(domain,message)→ string: like dgettext(), using preferred encoding ngettext(singular,plural,n)→ string: like gettext(), but consider plural forms (see Python and GNU gettext docs) lngettext(singular,plural,n)→ string: like ngettext(), using preferred encoding dngettext(domain,singular,plural,n)→ string: like ngettext(), looking in specified domain. ldngettext(domain,singular,plural,n)→ string: like dngettext(), using preferred encoding Generally _ is bound to gettext.gettext, and translatable strings are written in sources using _('thestring'). See docs for usage examples. Class based API The recommended way. Module gettext defines a class Translations, dealing with .mo translation files and supporting str/unicode strings. find(domain[,localedir[,languages[,all]]])→ str/None: .mo file name for translations (search in localedir/language/LC_MESSAGES/ translation(domain[,localedir[,languages[,class_[,fallback[,codeset]]]]]) →Translations: object from class class_ (default to GNUTranslations, constructor take file object as parameter) - if true fallback allow to return a NullTranslations if no .mo file is found, default to false (raise IOError) - codeset change charset used to encode translated strings install(domain[,localedir[,unicode[,codeset]]]) ➤ install _ function in Python's builtin namespace, to use _('thestring') Null Translations The NullTranslations is a base class for all Translations. t.__init__([fp]) ➤ initialize translations: fp is a file object - call _parse(fp) if it is not None t._parse(fp) ➤ nothing: subclasses override to read data from the file t.add_fallback(fallback) ➤ add fallback used if cannot found translation for a message Define methods gettext, lgettext, ngettext, lngettext as in the base API. And define speciale methods ugettext and ungettext returning unicode strings (other forms return encoded str strings). Return translated message, forwarding to fallback if it is defined. Overriden in subclasses.→ return protected _info attribute t.charset()→ return protected _charset attribute t.output_charset()→ return protected _output_charset attribute (defining encoding used to return translated messages) t.set_output_charset(charset) ➤ set _output_charset attribute t.install([unicode]) ➤ bind _ in builtin namespace to self.gettext() or self.ugettext() upon unicode (default to false) GNU Translations The GNUTranslations class (subclass of NullTranslations) is based on GNU gettext and .mo files. Messages ids and texts are coerced to unicode. Protected _info attribute contains message translations. Translation for empty string return meta-data (see doc). Define methods gettext, lgettext, ugettext, ngettext, lngettext, ungettext as in NullTranslations interface - same rules for return values (str/unicode). Message translations are searched in catalog, then in fallback if defined, and if no translation is found, message itself is returned (for n… methods, return singular forms if n=1 else plural forms). CONTAINERS Basic containers kind : -sequences (ordered collections) : list, tuple,str, any iterable,… -mappings (unordered key/value) : dict… -sets (unordered collections) : set, frozenset… Operations on Containers For strings, items are chars. For mappings, items are keys. item in container → bool: test item ∈ container1 item not in container → bool: test item ∉ container1 7a 7b 7c for var in container: … ➤ iterate var over items of container len(container) → int: count number of items in container2 max(container) → value: biggest item in container min(container) → value: smallest item in container sum(container) → value: sum of items (items must be number-compatible) 1 For strings test if expr is a substring of sequence. 2 Container must provide direct length method - no generator. Copying Containers Default containers constructors build new container with references to existing objects (shallow copy). To duplicate content too, use standard module copy. See Copying Objects (p3). Overriding Containers Operations __len__(self)→ int: called for len(self) __contains__(self,item)→ bool: called for item [not] in self You can override iterable protocol on containers too. SEQUENCES Sequences are ordered collections : str, unicode, list, tuple, buffer, xrange, array.array… any user class defining sequences interface, or any iterable data. Lists & Tuples Builtin types list and tuple store sequences of any objects. Lists are mutable, tuples are immutable. Declare a list : [item[,…]] Declare a tuple : (item[,…]) Notes : [] ➤ empty list ;() ➤ empty tuple ; (item,) ➤ one item tuple. list(object) → list: new list (cast from object / duplicate existing) tuple(object) → tuple: new tuple (cast from object / duplicate existing) range([start,]stop[,step])→ [int]: list, arithmetic progression of integers xrange1([start,]stop[,step]) → xrange: object generating arithmetic progression of integers Unless using a sequence as a mapping key, or ensuring it is immutable data, prefer list to tuple. 1 Use in place of range to avoid building huge lists just for indexing. Operations on Sequences See Operations on Containers (p7) too. seq1 + seq2 → concatenation of seq1 and seq2 sequence * n → concatenation of sequence duplicated n times n * sequence → concatenation of sequence duplicated n times reversed(sequence)→ iterator throught sequence in reverse order sorted(sequence[,cmp[,key[,reverse]]])→ list: new list, sorted items from iterable - see list.sorted() filter1(fct,sequence)→ list: new list where fct(item) is True. Use None fct for a boolean test on items map1(fct,sequence,…)→ list: new list where ith item is fct(ith items of sequence(s)) reduce(fct,sequence[,initializer])→ value: fct applied cumulatively to sequence items, f(f(…f(f(f(initializer,a),b),c,…) zip1(sequence,…)→ list: list of tuples, ith tuple contains ith items of each sequences 1 See Iteration Tools (p9) as replacement (avoid creating a new list). Indexing Use index [i] and slice [i:j[:step]] syntax. Indexs zero-based. Negative indexs indexing from end. Default step is 1, can use negative steps. Sub-sequences indexs between items. l = [e1,e2,e3,…,en-2,en-1,en] l[0]→ e1 l[1]→ e2 l[-2]→ en-1 l[-1]→ en l[0:n]→[e1,e2,e3,…,en-2,en-1,en] l[:]→[e1,e2,e3,…,en-2,en-1,en] l[i:]→[ei+1,ei+2,ei+3,…,en-1,en] l[:i]→[e1,e2,…,ei-2,ei-1,ei] items indexs -n -n+1 -n+2 … -2 -1 0 1 2 … n-2 n-1 e1 e2 e3 …item… en-1 en 0 1 2 3 … n-2 n-1 n -n -n+1 -n+2 -n+3 … -2 -1 slicing indexs Slice objects Defines index range objects, usable in [] notation. slice([start,]stop[,step])→ slice object slice.indices(len)→ (int{3}): (start,stop,stride) Ordered sets of data indexed from 0. Members start, stop, step. Extended Slicing Multiple slices notation - corresponding to a selection in a multi- dimension data - can be written using notation like [ a , x:y:z , : , : , : , m:n ]. Ellipsis notation can be used to fill multiple missing slices, like [ a , x:y:z , ... , m:n ]. See docs. Three dot notation ... is replaced internally by Ellipsis object. Operations on mutable sequences Mutable sequences (ex. list) can be modified in place. Can use mutable sequence indexing in left part of assignment to modify its items : seq[index]=expr ; seq[start:stop]=expr ; seq[start:stop:step]=expr seq.append(item) ➤ add item at end of sequence seq.extend(otherseq) ➤ concatenate otherseq at end of sequence seq.count(expr) → int: number of expr items in sequence seq.index(expr[,start[,stop]])→ int: first index of expr item seq.insert(index,item) ➤ item inserted at index seq.remove(expr) ➤ remove first expr item from sequence seq.pop([index]) → item: remove and return item at index (default -1) seq.reverse() ➤ items reversed in place seq.sort([cmp][,key][,reverse]) ➤ items sorted in place - cmp : custom comparison fct(a,b), retval <0 or = 0 or >0 - key : name of items attribute to compare - reverse : bool del seq[index] ➤ remove item from sequence del seq[start:stop[:step]] ➤ remove items from sequence Overriding Sequences Operations __getitem__(self,index2)→ value: item at index, called for self[index] __setitem__1(self,index2,value) ➤ set item at index to value, called for self[index]=value __delitem__1(self,index2) ➤ remove item at index, called for del self[index] 1 Only for mutable sequences. 2 Parameter index can be a slice [start,stop,step] - replace old __getslice__, __setslice__, __delslice__. Can also override arithmetic operations __add__ (concatenation ) and __mul__ (repetition ), container operations and object operations. MAPPINGS (DICTIONARIES) Builtin type dict. Store key:value pairs. Declare a dictionary : { key : value [,…]} {} dict()→ dict: empty dictionary (like {}) dict(**kwargs)→ dict: from named parameters and their values dict(iterable)→ dict: from (key,value) by iterable dict(otherdict)→ dict: duplicated fro another one (first level) Operations on Mappings See Operations on Containers (p7) too, considering operations on keys. d[key]→ value for key1 d[key]=value ➤ set d[key] to value del d[key] ➤ removes d[key] from d1 d.fromkeys(iterable[,value=None]) → dict: with keys from iterable and all same value d.clear() ➤ removes all items from d d.copy() → dict: hallow copy of d d.has_key(k)→ bool: test key presence - same as k in d d.items()→ list: copy of d's list of (key, item) pairs d.keys()→ list: copy of d's list of keys d.update(otherd) ➤ copy otherd pairs into d d.update(iterable) ➤ copy (key,value) pairs into d d.update(**kwargs) ➤ copy name=value pairs into d d.values()→ list: copy of d's list of values d.get(key,defval)→ value: d[key] if key∈d, else defval d.setdefault(key[,defval=None]) → value: if key∉d set d[key]=defval, return d[key] d.iteritems()→ iterator over (key, value) pairs d.iterkeys()→ iterator over keys d.itervalues()→ iterator over values d.pop(key[,defval]) → value: del key and returns the corresponding value. If key is not found, defval is returned if given, otherwise KeyError is raised d.popitem() → removes and returns an arbitrary (key, value) pair from d 1 If key doesn't exist, raise KeyError exception. Overriding Mapping Operations __getitem__(self,key)→ value for key, called for self[key] __setitem__(self,key,value) ➤ set value for key, called for self[key]=value __delitem__(self,key,value) ➤ remove value for key, called for del self[key] Can also override container operations and object operations. Other Mappings For on-disk mappings, see standard module shelve, and database modules . For ordered mappings see third party modules OrderedDict. SETS Unordered collections of unique items. Frozen sets are immutable once created. set([iterable]) → set: using values from iterable frozenset([iterable]) → frozenset: using values from iterable Operations on Sets See Operations on Containers (p7) too. s.issubset(others)→ bool: test s ⊂ others s.issuperset(others)→ bool: test others ⊂ s s.add(item) ➤ add item to set s.remove(item) ➤ remove item from set1 s.clear() ➤ emoves all items from (not forzen) set s.intersection(others)→ set: s ∩ others s & others → set: s ∩ others s.union(others) → set: s ∪ others s | others → set: s ∪ others s.difference(others) → set: [x / x∈s and x∉others] s - others → set: [x / x∈s and x∉others] s.symmetric_difference(others)→ set: [x / x∈s xor x∈others] s ^ others → set: [x / x∈s xor x∈others] s.copy()→ set: shallow copy of s s.update(iterable) ➤ adds all values from iterable to s 1 Raise KeyError if object not in set. Results set have same type as s object (set/frozenset). 8a 8b 8c OTHER CONTAINERS STRUCTURES, ALGORITHMS Generally containers follow Python idioms, you can use : len(cont), cont[i], for item in cont:… Array Standard module array provides efficient array of basic types. It uses compact storage for elements of same type. Type Codes n tc C type py type n tc C py type 1 'b' signed char int 1 'B' unsigned char int 1 'c' char str 2 'u' unicode char unicode 2 'h' signed short int 2 'H' unsigned short int 2 'i' signed int int 2 'I' unsigned int long 4 'l' signed long int 4 'L' unsigned long long 4 'f' float float 8 'd' double float n=size in bytes, tc=char typecode to use Functions array(tc,[iterable]) → array: with typecode tc, initialized from iterable a.typecode → str: typecode of a data a.itemsize → int: bytes size of a data a.append(expr) ➤ append item expr to end of a a.extend(array) ➤ append items from another array a.count(expr) → int: number of expr items a.index(expr) → int: first index of expr item a.insert(index,expr) ➤ expr item inserted at index a.remove(expr) ➤ remove first expr item a.pop([index]) → value: return and remove item at index (default -1) a.reverse() ➤ items in array are reversed a.buffer_info() → (int{2}): current storage infos (address,items count) a.byteswap() ➤ swap bytes of array items a.fromfile(f,n) ➤ append n items read from real binary file f1 a.tofile(f) ➤ write all items to real binary file f a.fromlist(list) ➤ extend array from values in list a.tolist() → list: items in a list a.fromstring(s) ➤ extend array from values in binary buffer s (string) a.tostring() → str: items in binary representation a.fromunicode(s) ➤ extend 'u' array from data in unicode stirng a.tounicode() → unicode: convert 'u' array to unicode string 1 If less items than needed, get available ones then raise EOFError. Old methods read and write replaced by fromfile and tofile. Queue Standard module collections provides queues management. deque([iterable])→ deque: initialized from iterable q.append(x) ➤ add x to right side of deque q.appendleft(x) ➤ add x to left side of deque q.clear() ➤ remove all elements from deque q.extend(iterable) ➤ extend right side of deque with iterable items q.extendleft(iterable) ➤ extend left side of the deque with iterable items q.pop() → item: pop and return item from dequeue right side q.popleft() → item: pop and return item from dequeue left side q.rotate(n) ➤ rotate deque from n steps, to right if n>0, to left if n<0 Can also use standard operations on sequences : len(q), reversed(q), copy.copy(q), copy.deepcopy(q), item in q, q[-1], and serialization via pickling protocol. Priority Queues Standard module heapq. Structure a list as a priority queue. heapify(x) ➤ transform list x into heap heappush(heap,item) ➤ push item onto heap heappop(heap)→ item: pop and return smallest item from the heap heapreplace(heap,newitem)→ item: pop and return smallest item from the heap, push newitem nlargest(n,iterable)→ list: n largest from iterable nsmallest(n,iterable)→ list: n smallest items from iterable Sorted List Standard module bisect maintains lists sorted (via basic bisection algo). bisect_left(list,item[,lo[,hi]])→ int: index to insert item at leftmost sorted position1 bisect_right(list,item[,lo[,hi]])→ int: index to insert item at rightmost sorted position1 bisect(…) ➤ alias for bisect_right(…) insort_left(list,item[,lo[,hi]]) ➤ insert item at leftmost sorted position1 insort_right(list,item[,lo[,hi]]) ➤ insert item at rightmost sorted position1 insort(…) ➤ alias for insort_right(…) 1 With list previously sorted. Iteration Tools Standard module itertools provides some practical iterators. chain(iterable[,…])→ iterator over items of several iterables count([start])→ iterator over integers from start (default 0) cycle(iterable)→ iterator cycling over iterable items dropwhile(predicatefct,iterable)→ iterator over items of iterable where predicatefct(item) is false groupby(iterable[,keyfct])→ iterator over (key value,group1 of items where keyfct(item)=key value), default keyfct is identity ifilter(predicate,iterable)→ iterator over items of iterable where predicatefct(item) is true - None predicate filter items being true ifilterfalse(predicate,iterable)→ iterator over items of iterable where predicatefct(item) is false - None predicate filter items being false imap(function,iterable[,…])→ iterator over function(items at same index from iterables2), None function return tuples items islice(iterable,[start,]stop[,step])→ iterator over items at slice3 indexs from iterable, None stop goes up to end izip(iterable[,…])→ iterator over tuple(items at same index from iterables) repeat(object[,count])→ iterator returning object over and over again, up to count times (default to infinite) starmap(function,iterable)→ iterator over function(*tuple item from iterable) takewhile(predicatefct,iterable)→ iterator over items of iterable where predicatefct(item) is true tee(iterable[,n]) → n independent iterators from same iterable4, default n=2 1 Group of items is internally used - must save it as list if needed after current iteration. 2 Stop at end of shorter iterable. 3 Slice parameters cannot be negative. 4 Don't use iterable out of tee created iterators. DATE & TIME Module time Standard module time defines common functions and data. Date & Time Data • float_time = float containing seconds from 'epoch' (january 1 1970 on Unix - see gmtime(0)), with sub-second precision in decimal part. • tuple_time = tuple containing 9 int (see table). • struct_time = tuple/object with int attributes (see table). # attribute value # attribute value 0 tm_year int 5 tm_sec 0…61 1 tm_mon 1…12 6 tm_wday 0…6 (monday=0) 2 tm_mday 1…31 7 tm_yday 0…366 3 tm_hour 0…23 8 tm_isdst 4 tm_min 0…59 0 (no) 1 (yes) -1 (unknown) • float_delay = float containing seconds, with sub-second precision. DST is local time, UTC is universal (GMT) time. accept2dyear → [rw] bool: accept two-digit year values (default true), modifiable via environment var PYTHONY2K altzone → int: offset (pos/neg) in seconds of DST relatively to UTC, in seconds, use only if daylight is true daylight → int: ≠0 if a DST timezone is defined timezone → int: offset (pos/neg) in seconds of local (non DST) timezone tzname → (str{2}): names of local timezone (non-DST, DST) Functions asctime([t=2])→ str: build local time string from t (tuple_time or struct_time) clock()→ float: processor time in seconds, for accurate relative time measurement ctime([secs=2])→ str: build local time string from float_time second gmtime([secs=2])→ struct_time: convert float_time to UTC struct_time localtime([secs=2])→ struct_time: convert float_time to DST struct_time mktime(t)→ float_time: convert DST t (tuple_time or struct_time) to float_time - may raise OverflowError or ValueError sleep(secs) ➤ execution suspended during secs (float_delay) times, maybe less (signal catching), may be more (process/threads scheduling) strftime(format[,t=2]) → str: build time string from t (tuple_time or struct_time) using format string (table infra) - may raise ValueError strptime(string[,format]) → struct_time: parse string using time format1 - may raise ValueError time() → float_time: current UTC time tzset() ➤ resets time conversion rules accordingly to environnment variable TZ - unix only, see docs 1 Default format "%a %b %d %H:%M:%S %Y". Missing values default to (1900, 1, 1, 0, 0, 0, 0, 1, -1) 2 Param secs default to current time, param t default to local current time. Time format strings %a Abbreviated weekday name1. %A Full weekday name1. %b Abbreviated month name1. %B Full month name1. %c Appropriate date and time representation1. %d Month day [01,31]. %H Hour [00,23]. %I Hour [01,12]. %j Year day [001,366]. %m Month [01,12]. %M Minute [00,59]. %p AM or PM1. %S Second [00,61]. %U Year week [00,53] (Sunday based). %w Week day [0,6] (0=Sunday). %W Year week [00,53] (Monday based). %x Appropriate date representation1. %X Appropriate time representation1. %y Year [00,99]. %Y Year (with century). %Z Time zone name (no characters if no time zone exists). %% Literal % char. 1 Locale language representation. Module datetime Standard module datetime has tools for date/time arithmetics, data extraction and manipulation. Defines class : timedelta, time, date, datetime, [tzinfo]. Module timeit Standard module timeit has functions to measure processing time of code. It can be used in scripts (see docs), or directly in command line : python -mtimeit [-n N] [-r N] [-s S] [-t] [-c] [-h] [statement […]] -n N / --number=N execute statement N times -r N / --repeat=N repeat timer N times (default 3) -s S / --setup=S executed S once initially (default pass) -t / --time use time.time() (default except Windows) -c / --clock use time.clock() (default on Windows) -v / --verbose print raw timing results - may repeat option -h / --help print help and exit 9a 9b 9c Other Modules Standard module calendar has functions to build calendars. See also third party module mxDateTime. FILES Normal file operations use Python file objects (or file-like objects with same interface). Some functions directly manipulate files path names (strings). Functions mapping low level OS handlers (mainly those in standard os module) use numeric file descriptors (fd also known as fileno). Raw data use str type (can contain any data byte values, including 0). File Objects Standard file type is builtin file. It defines the Python file protocol. Create a file : file(filename[,mode='r'[,bufsize]]) → file object Mode flags (combinable) : 'r' read, 'w' write new, 'a' write append, '+' update, 'b' binary1, 'U' universal newline2. Buffer size : 0 unbuffered, 1 line buffered, >1 around that size. Open() is an alias for file() 1 Default text mode tries to interpret newline sequences in the file. 2 Automatically choose newline sequence in CR or LF or CR+LF adapted from file/to platform. Methods and Functions f.close() ➤ file flushed and no longer usable f.fileno() → int: low level file descriptor (fd) f.flush() ➤ buffers written to file on disk f.isatty() → bool: indicator file is a terminal[size]) → str: block of data read from file f.readline() → str: next line read from file, end of line removed f.readlines() → [string]: list of all lines read from file, end of lines removed[,whence=0]) ➤ modify current position in file - whence: 0 from start, 1 from current, 2 from end f.tell() → int: current position in file f.write(string) ➤ data written to file f.writelines(listofstrings) ➤ data written to file (no end of line added) for line in f :… ➤ iterate line over lines of f Old method xreadlines replaced by iteration on file object. For optimized direct access to random lines in text files, see module linecache. Attributes f.closed → bool: indicator file has been closed f.encoding → str/None: file content encoding → str: name of the file f.newlines → str/tuple of str/None: encountered newlines chars f.softspace → bool: indicator to use soft space with print in file Low-level Files Base low-level functions are in standard module os. Careful of clash with builtins with name. open(path,flags[,mode=0777])→ int (fd): open file path - see flags infra - mode masked out with umask fdopen(fd[,mode[,bufsize]]) → file: build a file connected to fd - mode and bufsize as for builtin open()+ mode must start with r or w or a dup(fd)→ int (fd): duplicate file descriptor fd dup2(fd,fd2)→ int (fd): duplicate file descriptor fd into fd2, previously closing fd2 if necessary close(fd) ➤ close file descriptor read(fd,n)→ str: read as most n bytes from fd file - return empty string if end of file reached write(fd,str)→ int: write str to fd file - return number of bytes actually written lseek(fd,pos,how) ➤ set file descriptor position - how: 0 from start, 1 from current, 2 from end fdatasync(fd) ➤ flush file data to disk - don't force update metadata (Unix) fsync(fd) ➤ force low level OS buffers to be written ftruncate(fd,length) ➤ truncate file descriptor to at most length (Unix) Open Flags Constants defined in os module, use bit-wise OR (x|y|z) to mix them. O_RDONLY → read only O_WRONLY → write only O_RDWR → read/write O_APPEND → append each write to end O_CREAT → create new file (remove existing) O_EXCL → with O_CREAT, fail if file exist (Unix) O_TRUNC → reset existing file to zero size O_DSYNC → xxxxxx (Unix) O_RSYNC → xxxxxx (Unix) O_SYNC → return from IO when data are physically written (Unix) O_NDELAY → return immediatly (don't block caller during IO) (Unix) O_NONBLOCK → same as O_NDELAY (Unix) O_NOCTTY → terminal device file can't become process tty (Unix) O_BINARY → don't process end of lines (cf+lf from/to cr) (Windows) O_NOINHERIT → xxxxxx (Windows) O_SHORT_LIVED → xxxxxx (Windows) O_TEMPORARY → xxxxxx (Windows) O_RANDOM → xxxxxx (Windows) O_SEQUENTIAL → xxxxxx (Windows) O_TEXT → xxxxxx (Windows) Pipes For standard process redirection using pipes, see also Simple External Process Control (p14). os.pipe() → ((int{2}){2}): create pair (fdmaster,fdslav) of fd (read,write) for a pipe os.mkfifo(path[,mode=0666]) ➤ create named pipe path - mode masked out with umask - don't open it (Unix) Use os functions on file descriptors. In-memory Files Memory Buffer Files Use standard modules StringIO and cStringIO to build file-like objects storing data in memory. f = StringIO.StringIO() Build a file-like in memory. f.write(string) ➤ data written to file f.…other file writing methods… f.getvalue() → str: current data written to file f.close() ➤ file no longer usable, free buffer cStringIO is a compiled (more efficient) version of StringIO for writing. Optional argument allows to build memory files to read from too. f = cStringIO.StringIO([string])[size]) → str: block of data read from 'file' (string) f.…other file reading methods… Memory Mapped Files (OS level) Standard module mmap manage memory-mapped files, usable as file-like objects and as mutable string-like objects. To build a memory map : mm = mmap.mmap(fileno,length[,tagname[,access]]) [windows] mm = mmap.mmap(fileno,length[,flags[,prot[,access]]]) [unix] Use an os file descriptor (from or from file-object's fileno()) for a file opened for update. Length specify amount of bytes to map. On windows, file may be extended to that length if it is shorter, it can't be empty, and 0 correspond to maximum length for the file. Access (keyword param) : ACCESS_READ (readonly), ACCESS_WRITE (write-through, default on Windows), or ACCESS_COPY (copy-on-write). On Windows, tagname allow to identify different mappings against same file (default to None). On Unix, flags : MAP_PRIVATE (copy-on-write private to process) or MAP_SHARED (default). And prot (memory protection mask) : PROT_READ or PROT_WRITE, default is PROT_READ|PROT_WRITE. If use prot+flags params, don't use access param. mm.close() ➤ mmap file no longer usable mm.find(string[,start=0])→ int: offset / -1 mm.flush([offset,size]) ➤ write changes to disk mm.move(dest,src,count) ➤ copy data in file[size])→ str: block of data read from mmap file1 mm.read_byte()→ str: next one byte from mmap file1 mm.readline()→ str: next line read from file, end of line is not removed1 mm.resize(newsize) ➤ writable mmap file resizer[,whence=0]) ➤ modify current position in mmap file - whence: 0 from start, 1 from current, 2 from end mm.size()→ int: length of the real os file mm.tell() → int: current position in mmap file mm.write(string) ➤ data written to mmapfile1 mm.write_byte(byte) ➤ str of one char (byte) data written to mmap file1 1 File-like methods use and move file seek position. Files Informations Functions to set/get files informations are in os and in os.path module, some in shutil module. Constants flags are defined in standard stat module. Some functions accessing process environment data (ex. current working directory) are documented in Process section. os.access(path,mode)→ bool: test for path access with mode using real uid/gid - mode in F_OK, R_OK, W_OK, X_OK os.F_OK → access mode to test path existence os.R_OK → access mode to test path readable os.W_OK → access mode to test path writable os.X_OK → access mode to test path executable os.chmod(path,mode) ➤ change mode of path - mode use stat.S_* constants os.chown(path, uid, gid) ➤ change path owner and group (Unix) os.lchown(path, uid, gid) ➤ change path owner and group - don't follow symlinks(Unix) os.fstat(fd)→ int: status for file descriptor os.fstatvfs(fd)→ statvfs_result: informations about file system containing file descriptor (Unix) os.stat(path)→ stat structure object: file system informations (Unix) os.lstat(path)→ stat structure object: file system informations (Unix) - dont follow symlinks os.stat_float_times([newvalue])→ bool: test/set stat function time stamps data type - avoid setting new value os.statvfs(path)→ statvfs_result: informations about file system containing path (Unix) os.utime(path,times) ➤ set access and modification times of file path - times=(atime,mtime) (numbers) - times=None use current time os.fpathconf(fd,name) → str / int: system configuration information about file referenced by file descriptor - see platform documentation and pathconf_names variable - name str or int (Unix) os.pathconf(path,name)→ str / int: system configuration information about file referenced by file descriptor - see platform documentation and pathconf_names variable - name str or int (Unix) os.pathconf_names → dict: name → index - names accepted by pathconf and fpathconf → corresponding index on host (Unix) os.path.exists(path)→ bool: test existing path - no broken symlinks os.path.lexists(path)→ bool: test existing path - allow broken symlinks os.path.getatime(path)→ float_time: last access time of path os.path.getmtime(path)→ float_time: last modification time of path os.path.getctime(path)→ float_time: creation time (windows) or last 10a 10b 10c modification time (unix) of path os.path.getsize(path)→ int: bytes size of path file os.path.isabs(path)→ bool: test absolute os.path.isfile(path)→ bool: test regular file (follow symlinks) os.path.isdir(path)→ bool: test existing directory (follow symlinks) os.path.islink(path)→ bool: test symlink os.path.ismount(path)→ bool: test mount point os.path.samefile(path1,path2)→ bool: test refer to same real file (unix,macos) os.path.sameopenfile(f1,f2)→ bool: test opened files refer to same real file (unix,macos) os.path.samestat(stat1,stat2)→ bool: test stat tuples refer to same file (unix,macos) shutil.copymode(srcpath,dstpath) ➤ copy normal file permission bits shutil.copystat(srcpath,dstpath) ➤ copy normal file permission bits and last access and modification times Stat Structures stat_result is returned by stat and lstat functions, usable as a tuple and as object with attributes : # attribute usage 0 st_mode protection bits 1 st_ino inode number 2 st_dev device 3 st_nlink number of hard links 4 st_uid user ID of owner 5 st_gid group ID of owner 6 st_size size of file, in bytes 7 st_atime time of most recent access 8 st_mtime time of most recent content modification 9 st_ctime time of most recent metadata change on Unix, time of creation on Windows st_blocks number of blocks allocated for file (Unix) st_blksize filesystem blocksize (Unix) st_rdev type of device if an inode device (Unix) st_rsize size of resource fork, in bytes(MacOS) st_creator file creator code (MacOS) st_type file type code (MacOS) statvfs_result is returned by fstatvfsand statvfs functions, usable as a tuple (use statvfs variable indexs) and as an object with attributes : # attribute index var usage 0 f_bsize F_BSIZE preferred file system block size 1 f_frsize F_FRSIZE fundamental file system block size 2 f_blocks F_BLOCKS total number of blocks in the filesystem 3 f_bfree F_BFREE total number of free blocks 4 f_bavail F_BAVAIL free blocks available to non-super user 5 f_files F_FILES total number of file nodes 6 f_ffree F_FFREE total number of free file nodes 7 f_favail F_FAVAIL free nodes available to non-super user 8 f_flag F_FLAG flags - see host statvfs() man page 9 f_namemax F_NAMEMAX maximum file name length Stat Constants Defined in standard stat module. S_ISUID → xxxxx S_ISGID → xxxxx S_ENFMT → xxxxx S_ISVTX → xxxxx S_IREAD → 00400 user can read S_IWRITE → 00200 user can write S_IEXEC → 00100 user can execute S_IRWXU → 00700 user can read+write+execute S_IRUSR → 00400 user can read S_IWUSR → 00200 user can write S_IXUSR → 00100 user can execute S_IRWXG → 00070 group can read+write+execute S_IRGRP → 00040 group can read S_IWGRP → 00020 group can write S_IXGRP → 00010 group can execute S_IRWXO → 00007 everybody can read+write+execute S_IROTH → 00004 everybody can read S_IWOTH → 00002 everybody can write S_IXOTH → 00001 everybody can execute Terminal Operations os.openpty()→ (int{2}): open pseudo-terminal1 pair (fdmaster,fdslave)=(pty,tty) (Unix) os.ttyname(fd)→ str: terminal device associated to fd (Unix) os.isatty(fd)→ bool: test file descriptor is a tty-like (Unix) os.tcsetpgrp(fd,pg) ➤ set process group id associted with terminal fd (Unix) os.tcgetpgrp(fd)→ int: process group associated with terminal fd (Unix) See also standard modules tty and pty. For user-interface control on text terminal , see standard package curses and its sub-modules. Temporary Files Use standard tempfile module. It defines several functions to make life easier and more secure. TemporaryFile([mode='w+b'[,bufsize=-1[,suffix[,prefix[,dir]]]]]) → file/file-like: temp file - removed on close - not necessary visible in file-system - dir and prefix as for mkstemp NamedTemporaryFile([mode='w+b'[,bufsize=-1[,suffix[,prefix[,dir]]]]]) → file/file-like: like TemporaryFile - file visible in file-system mkstemp([suffix[,prefix[,dir[,text]]]])→ (int,str): (fd,path) of new temporaty file - no race condition - only creator can read/write - no executable bit - not automatically deleted - binary mode unless text specified mkdtemp([suffix[,prefix[,dir]]])→ str: path of new temporary directory created - no race condition - only creator can read/write/search - not automatically deleted gettempdir() → str: default directory for temporary files gettempprefix() → str: default filename prefix for temporary files Other functions in tempfile and os modules are kept for code compatibility, but are considered not enough secured. Also tempdir and template data in tempfile - which should not be used directly. Path Manipulations Path manipulation functions are in standard os.path module. supports_unicode_filenames → bool: unicode usable for file names abspath(path)→ str: normalized absolutized pathname basename(path)→ str: file name part of path commonprefix(pathlist) → str: longest common path prefix (char-by-char) dirname(path)→ str: directory name of pathname join(path[,…])→ str: concatenate path components normcase(path)→ str: normalize path case for platform (see doc) normpath(path)→ str: normalize path (// /./ /../), on windows /→ \ realpath(path)→ str: canonical path (remove symlinks) (unix) split(path)→ (str{2}): split into (head, last pathname component) splitdrive(path)→ (str{2}): split into (drive, tail) splitext(path)→ (str{2}): split into (root, ext) Host Specific Path Data sys.getfilesystemencoding() → str: name of encoding used by system for filenames Following data are in os and in os.path. curdir → str: string used to refer to current directory pardir → str: string used to refer to parent directory sep → str: char used to separate pathname components altsep → str: alternative char used to separate pathname components extsep → str: char used to separate base filename from extension pathsep → str: conventional char to separate different paths Directories os.listdir(path)→ [str]/[unicode]: list names in path directory - without . and .. - arbitrary order - path string type → item strings type os.mkdir(path[,mode=0777]) ➤ create directory path - mode masked out with umask os.makedirs(path[,mode=0777]) ➤ create directory path, recursively - mode masked out with umask - don't handle Windows' UNC path os.rmdir(path) ➤ remove directory path os.removedirs(path) ➤ remove directories, recursively os.walk(top[,topdown=True [,onerror=None]])→ iterable: go throught dirs under top, for each dir yield tuple(dirpath, dirnames, filenames) - onerror=fct(os.error) - see docs os.path.walk(path,visit,arg) ➤ call visit(arg,dirname,names) for dirs rooted at path - may modify names (files list) to influence walk, may prefer to use os.walk Special Files,dst) ➤ create hard link named dst referencing src (Unix) os.symlink(src,dst) ➤ create symbolic link named dst pointing to src (Unix) os.readlink(path)→ str: path pointed to by symbolic link os.mknod(path[,mode=0666,device]) ➤ create FS node (file, device special file, named pipe) - mode = permissions | nodetype - node type in S_IFREG, S_IFREG, S_IFCHR, S_IFBLK, and S_IFIFO defined in stat module os.major(device) → int: raw device major number os.minor(device) → int: raw device minor number os.makedev(major,minor) ➤ compose raw device from major and minor numbers Copying, Moving, Removing os.remove(path) ➤ remove file path (not directory) os.rename(src,dst) ➤ rename src to dst - on same filesystem- may remove existing dst file os.renames(old,new) ➤ rename old to new, recursively - try to create intermediate directories os.unlink(path) ➤ remove file path (not directory) - same as remove Standard module shutil provides high level functions on files and directories. copyfile(src,dst) ➤ copy normal file content - overwrite destination2. copyfileobj(fsrc,fdst[,length=16kb]) ➤ copy file-like object content by blocks of length size (<0=one chunk) copy(src,dst) ➤ copy normal file content to file/directory2 - in case of directory use same basename as src - overwrite destination - copy permission bits. copy2(src,dst) ➤ same as copy + copy last access and modification times2. copytree(src,dst[,symlinks=False]) ➤ recursively copy directory tree - destination must be new - files copied via copy - if symlinks is False, copy symbolic links files content, else just make symbolic links.1 rmtree(path[,ignore_errors=False[,onerror=None]]) ➤ recursively delete directory tree - onerror=fct(fctref, path, excinfo).1 move(src,dst) ➤ recursively move file or directory tree - may rename or copy.1 1 May raise shutil.Error exception. 2 Params src and dst are files path names. Encoded Files Standard module codecs have functions and objects to transparently process encoded files (used internally as unicode files).,mode[,encoding[,errors[,buffering]]])→ file-like EncodedFile object with transparent encoding/decoding codecs.EncodedFile(file,input[,output[,errors]]) → file-like wrapper around file, decode from input encoding and encode to output encoding codecs.BOM → str: alias for BOM_UTF16 codecs.BOM_BE → str: alias for BOM_UTF16_BE 11a 11b 11c codecs.BOM_LE → str: alias for BOM_UTF16_LE codecs.BOM_UTF8 → str: '\xef\xbb\xbf' codecs.BOM_UTF16 → str: alias for BOM_UTF16_LE or BOM_UTF16_BE codecs.BOM_UTF16_BE → str: '\xfe\xff' codecs.BOM_UTF16_LE → str: '\xff\xfe' codecs.BOM_UTF32 → str: alias for BOM_UTF32_LE or BOM_UTF32_BE codecs.BOM_UTF32_BE → str: '\x00\x00\xfe\xff' codecs.BOM_UTF32_LE → str: '\xff\xfe\x00\x00' See Encoding - Decoding (p12) for details about encoding and errors. Serialization Standard modules pickle and cPickle (speed up to 1000x) have support for data serialization of objects hierarchies. See Python documentation. See also module marshal (read/write of Python data in platform independant binary format - but can broke format between releases). Persistence Standard module shelve use pickling protocol to store objects in DBM files (see p17) and access them via a dictionnary-like interface with keys as str. open(filename[,flag[,protocol[,writeback[,binary]]]])→ dictionary-like object - flag as (p17), default to 'c' - protocol default to 0 (ascii format) - writeback: cache accessed entries in memory and written them back at close time, default to False - binary is deprecated, use protocol. Configuration Files Standard module ConfigParser. It uses standard .INI files to store configudation data : [section] name:value name=value Values can contain %(name)s references which may be expanded using values in same section or in defaults # and ; start comment lines. Module defines 3 configuration classes with different data access level : RawConfigParser ConfigParser SafeConfigParser rp=RawConfigParser([defaults]) → RawConfigParser cp=ConfigParser([defaults]) → ConfigParser sp=SafeConfigParser([defaults]) → SafeConfigParser In the three constructors, defaults is a dict of option:value for references expansion. MAX_INTERPOLATION_DEPTH → int: max recursive depth for get() when raw parameter is false DEFAULTSECT → str: name of defaut section Raw Interface rp.defaults()→ dict: default values for references expansion rp.sections()→ [string]: list sections in config (without DEFAULT) rp.add_section(section) ➤ add a new section - may raise DuplicateSectionError rp.has_section(section)→ bool: test if section exists - cant test for DEFAULT rp.options(section)→ [string]: list options in section rp.has_option(section,option)→ bool: test if section and option exists[filename]/filename)→ [filename]: try to load configuration data from files (continue if fail) - return names of loaded files rp.readfp(fp[,filename]) ➤ load configuration data from file/file-like rp.get(section,option)→ str: option value rp.getint(section,option)→ int: coerce option value to int rp.getfloat(section,option)→ float: coerce option value to float rp.getboolean(section,option)→ bool: coerce option value to bool - True is strings 1 yes true on - False is strings 0 no false off - may raise ValueError rp.items(section)→[(name,value)]: options in the section rp.set(section,option,value) ➤ set option to string value in section - may raise NoSectionError rp.write(fileobject) ➤ write configuration data to file rp.remove_option(section,option)→ bool: return True if there was such option - may raise NoSectionError rp.remove_section(section)→ bool: return True if there was such section rp.optionxform(option)→ str: normalized internal form of option Normal Interface cp.get(section,option[,raw[,vars]])→ string: value for option in section - % interpolation expanded unless raw is true - vars is a dict of additional defaults - reference expansion names are processed by optionxform() for matching cp.items(section[,raw[,vars]])→ [(name,value)]: for given section - raw and vars as in get() Safe Interface sp.set(section,option,value) ➤ set value string for section and option Exceptions (Exception) Error ParsingError NoSectionError DuplicateSectionError MissingSectionHeaderError NoOptionError InterpolationError InterpolationDepthError InterpolationMissingOptionError InterpolationSyntaxError For similar file format supporting nested subsections, see ConfigObj config parser. For windows users, standard module _winreg. For text-file configs, can use XML tools, and see also third party YAML parsers like PyYaml. EXCEPTIONS Standard exceptions defined in exceptions module, and available in current scope. All exceptions must be subclasses of Exception root class. Use standard exceptions if their meaning correspond to you errors. Subclass standard exceptions when needed. Standard Exception Classes Exception StopIteration ― iterator's next(), no more value. SystemExit ― sys.exit() called StandardError ― built-in exceptions ArithmeticError ― arithmetic errors. FloatingPointError OverflowError ZeroDivisionError AssertionError ― assert cond[,message] failed. AttributeError ― attribute set/get failed. EnvironmentError ― host system error - see arg tuple attribute IOError OSError WindowsError ― Windows error codes. EOFError ― end-of-file with input() or raw_input(). ImportError KeyboardInterrupt ― user interrupt (Ctrl-C). LookupError IndexError ― non-existent sequence index. KeyError ― non-existent mapping key. MemoryError NameError ― non-existent name in current scope. UnboundLocalError ― reference to an unassigned local variable. ReferenceError ― try accessing weak-ref disposed object. RuntimeError ― (prefer defining ad-hoc subclasses). NotImplementedError SyntaxError IndentationError TabError SystemError ― a bug… in Python. TypeError ValueError ― good type, but bad value. UnicodeError Warning ― warnings superclass (see Warnings infra) UserWarning PendingDeprecationWarning DeprecationWarning SyntaxWarning RuntimeWarning Warnings Warnings must be subclasses of Warning root class. Standard warnings module control processing of warning exceptions. warn(message[,category[,stacklevel]]) warn_explicit(message,category,filename,lineno[,module[,registry]]) showwarning(message,category,filename,lineno[,file]) formatwarning(message,category,filename,lineno) filterwarnings(action[,message[,category[,module[,lineno[,append]]]]]) resetwarnings() sys.warnoptions Exceptions Processing sys.exc_info()→ (type,value,traceback) for current exception1 sys.exc_clear() ➤ current exception related informations cleared sys.excepthook → (rw) fct(type, value, traceback) called for uncaught exceptions sys.__excepthook__ → backup of original excepthook function sys.tracebacklimit → int: (rw) maximum levels of traceback printed, <=0 for none 1 Or (None,None,None) if no running exception. Standard module traceback has tools to process and format these informations. ENCODING - DECODING Standard module codecs provide base support for encoding / decoding data. This is used for character encodings, but also for data compression (zip, bz2) or data representation (uu, hex). See Unicode strings (p5), Source encodings (p3). See functions, classes and constants for files encoding in Encoded Files (p11). Module encodings.aliases. THREADS & SYNCHRONIZATION Python threads use native threads. A global mutex (the GIL) lock interpreter data during Python virtual instructions execution (it is unlocked during I/O or long computation in native code). Check for thread switching and signal processing is performed at regular interval. sys.getcheckinterval()→ int: current thread switching check interval1 sys.setcheckinterval(interval) ➤ set hread switching check interval1 1 Expressed in number of Python virtual instructions. Threading Functions Use standard high level module threading which provides several classes : Thread, local (for thread local storage), Event, Lock and RLock (mutex), Semaphore and BoudedSemaphore, Timer. Module threading also provides functions : activeCount()→ int: number of currently active threads currentThread()→ Thread: current running thread enumerate()→ [Thread]: list of active threads 12a 12b 12c settrace(func) ➤ install trace function called before threads run methods setprofile(func) ➤ install profile function called before threads run methods Standard module thread supports low level thread management. Use modules dummy_thread and dummy_threading on platforms without multithreading. Threads Class threading.Thread is used to create new execution path in current process. It must be called with keyword arguments. Specify thread code with a callable target param or by overriding run method (remember calling inherited __init__ in subclasses), give arguments in args and kwargs (tuple and dict), give a name to identify the thread - group currently not used (None). th = threading.Thread(group,target,name,args,kwargs) th.start() ➤ start thread activity (in another thread) ➤ thread code to execute - call target if not overriden th.join([timeout]) ➤ wait for th termination or timeout elapsed (float_delay, default to None for infinite) th.getName()→ str: thread associated name th.setName(name) ➤ set thread associated name (initial name set by class) th.isAlive()→ bool: test thread alive (started and run() not terminated) th.isDaemon()→ bool: test thread have daemon flag th.setDaemon(daemonic) ➤ set thread daemon flag - must be called before start. Initial flag inherited from creating thread. Python process exit only after last non-daemon thread termination. A thread can't be killed or paused externally by another thread. Thread Local Storage Class threading.local attributes values are thread local. Subclass it or use it as a namespace. tlsdata = threading.local() tlsdata.x = 1 Delayed Start Thread Class threading.Timer is a subclass of Thread which effectively run after a specified interval from its start. t = threading.Timer(interval,function,args=[],kwargs={}) t.cancel() ➤ timer will never run - must not be already running Create a timer that will run function with arguments args and keyword arguments kwargs, after interval seconds have passed. Mutual Exclusion Classes threading.Lock and threading.RLock provide mutual exclusion between threads. Lock doesn't allow a thread to re-acquire a lock it already owns, RLock does (reentrant-lock). lock = threading.Lock() lock = threading.RLock() lock.acquire([blocking])→ bool/None: acquire the lock. blocking unspecified : wait & return None ; blocking true : wait & return True ; blocking false : don't wait (try) & return True/False lock.release() ➤ unlock a previously acquired lock Must release a lock same times as it was acquired. Good practice to acquire/release locks in try/finally blocks. For portable inter-process mutex, see third party module. Events Class threading.Event is a synchronisation flag with thread blocking mechanism to wait for the flag. evt = threading.Event() ➤ new event, with internal flag set to False evt.isSet()→ bool: value of event internal flag evt.set() ➤ set event internal flag to true - unlock waiting threads evt.clear() ➤ set event internal flag to False evt.wait([timeout]) ➤ wait for event internal flag to be true - timeout is a float_delay (default to None=infinite blocking) General purpose events scheduler Module sched provides such a tool, adaptable to your needs ('time' unit is yours). sc = sched.scheduler(timefunc,delayfunc) → scheduler: timefunc return numbers mesuring time, delayfunc(n) wait n time (same unit as timefunc output) - typically sc = sched.scheduler(time.time,time.sleep) sc.enterabs(time,priority,action,args) → evtid: schedule a new event, will call action(*args) at time sc.enter(delay,priority,action,args)→ evtid: schedule a new event, will call action(*args) after delay sc.cancel(evtid)➤ remove scheduled event - may raise RuntimeError sc.empty()→ bool: test if scheduler events queue is empty➤ run scheduled events at their scheduling time - see docs Semaphores Classes threading.Semaphore and threading.BoundedSemaphore provide simple semaphore for resources counting (without/with counter checking). sem = threading.Semaphore([value=1]) ➤ semaphore with initial counter sem = threading.BoundedSemaphore([value]) sem.acquire([blocking])→ bool/None: acquire the semaphore (consume one resource). blocking unspecified : wait & return None ; blocking true : wait & return True ; blocking false : don't wait (try) & return True/False sem.release() ➤ release the semaphore (free one resource) Condition Variables Class threading.Condition allows threads to share state (data) protected via a Lock. Important : condition variables (lock) must be acquired when calling wait, notify or notifyAll. See Python docs. cond = threading.Condition([lock]) ➤ build new condition variable, use user providen lock (Lock or RLock) else build a new RLock cond.acquire(*args)→ value: acquire cond. var. lock, return lock.acquire() value cond.release() ➤ release cond. var. lock cond.wait([timeout]) ➤ wait until notified or timeout elapsed- timeout is a float_delay (default to None=infinite blocking). Release cond. var. lock and wait for a notification/timeout then re-acquire lock. cond.notify() ➤ wake up one waiting thread (if any). cond.notifyAll() ➤ wake up all waiting threads. Synchronized Queues Module Queue provides a class Queue to store data in a synchronized FIFO queue, and two exception classes Full and Empty. In blocking mode, full queue block producers and empty queue block consumers (in non-blocking mode they raise exceptions). Other organization can be built with subclassing (see source for internal methods). q = queue.Queue(maxsize) ➤ build new queue - infinite queue if maxsize<=0 q.qsize()→ int: size of the queue - at call time q.empty()→ bool: test if queue size if 0 - at call time q.full()→ bool: test if queue size is maxsize - at call time q.put(item[,block[,timeout]]) ➤ put item in queue - block can be true/false, timeout can be None/float_delay. May raise Queue.Full exception. q.put_nowait(item) ➤ same as put(item,False) q.get([block[,timeout]])→ item: removed from queue - block can be true/false, timeout can be None/float_delay - may raise Queue.Empty exception q.get_nowait() ➤ same as get(False) PROCESS Current Process Standard module os has tools to get information about and manipulate current process and its environment. Exiting Normally Python process exit when there is no more non-daemon thread running. sys.exit([arg=0]) ➤ exit via a SystemExit exception (may be catch) - arg is exit code os._exit(n) ➤ exit without cleanup os.abort() ➤ exit via a SIGABRT signal (signal may be handled) Following exit codes are defined in os (Unix) : EX_OK no error EX_USAGE command used incorrectly EX_DATAERR incorrect input data EX_NOINPUT unavailable/inaccessible input EX_NOUSER unknown user EX_NOHOST unknown host EX_UNAVAILABLE required service unavailable EX_SOFTWARE internal error EX_OSERR OS error EX_OSFILE missing/inaccessible file EX_CANTCREAT can't create output EX_IOERR error during file I/O EX_TEMPFAIL temporary failure EX_PROTOCOL illegal/invalid/not understood protocol exchange EX_NOPERM not enough permissions (out of file perms) EX_CONFIG configuration problem EX_NOTFOUND missing data You can install exit functions (for normal exit) with module atexit. register(func[,*args[,**kargs]]) ➤ register function to be called with args and kargs Registered functions are called in reverse order of registration. Bypassed when process is terminated by a signal, an internal error, or an os._exit. Environment Variables environ → dict: environment variables - modification call putenv if supported getenv(varname[,default=None])→ str: environment variable value putenv(varname,value) ➤ set environment variable - affect later started subprocess - may cause memory leaks (see platform documentation) Some functions also in os.path : expanduser(path)→ str: path with initial "~" or "~user" replaced expandvars(string)→ str: string with $name or ${name} environment variable replaced Directory, Files, Terminal See also Console & Interactive Input/Output (p1), and Files - Terminal Operations (p11). chdir(path) ➤ change current working directory to path fchdir(fd) ➤ change current working directory to thus represented by file descriptor getcwd()→ str: current working directory getcwdu()→ unicode: current working directory chroot(path) ➤ change process file-system root to path (Unix) umask(mask)→ int: set current numeric umask and return previous one ctermid()→ str: filename of controlling terminal (Unix) getlogin()→ str: name of user logged on controlling terminal (Unix) User, process, group IDs pid: process id, gid: group id, uid: user id getpid()→ int: current pid getegid()→ int: effective gid (Unix) setegid(egid) ➤ set process effective gid (Unix) geteuid()→ int: effective uid (Unix) seteuid(euid) ➤ set process effective uid (Unix) getgid()→ int: real gid (Unix) setgid(gid) ➤ set process gid (Unix) getuid()→ int: current process' uid (Unix) setuid(uid) ➤ set process current uid (Unix) 13a 13b 13c setregid(rgid,egid) ➤ set process real and effective gid (Unix) setreuid(ruid,euid) ➤ set process real and effective uid (Unix) getpgrp()→ int: current gid (Unix) getgroups()→ [int]: list of supplemental associated gid (Unix) setgroups(groups) ➤ set list of supplemental associated gid (Unix) setpgrp() ➤ call system function1 (Unix) getppid()→ int: parent's pid (Unix) setsid() ➤ call system function1 (Unix) getpgid(pid)→ int: process group id of process id pid (0=current) (Unix) getsid(pid) ➤ call system function1 (Unix) setpgid(pid,pgrp) ➤ set process pid group to pgrp1 (Unix) 1 See manual for semantics. Timings, Priority times()→ (ut,st,cut,cst,ert): (float_delay{5}): user time, system time, children's user time, children's system time, elapsed real time nice(increment)→ int: renice process - return new niceness (Unix) Memory plock(op) ➤ lock program segments into memory - see for op values (Unix) Host Informations strerror(code)→ str: error message for the error code uname()→ tuple: current operating system identification, (sysname, nodename, release, version, machine) (recent Unix) sys.byteorder → str: host native byte order big or little sys.winver → str: version number for registry keys (Windows) sys.platform → str: platform identifier (ex. linux2) Following data are in os and in os.path. defpath → str: search path for os.exec*p*() and os.spawn*p*() if environment PATH not defined linesep → str: end of line char(s) for the plaftorm devnull → str: file path of null device Python Informations sys.builtin_module_names → (str): names of modules compiled into interpreter sys.copyright → str: copyright of interpreter sys.hexversion → int: Python version with one digit by byte sys.version → str: interpreter version + build + compiler sys.dllhandle → int: handle of Python DLL (Windows) sys.executable → str: name of interpreter executable binary sys.prefix → str: directory prefix for platform independant Python files sys.api_version → int: version of Python C API sys.version_info → (int{3},str,int): (major, minor, micro, releaselevel, serial) - release in alpha, beta, candidate, final Signal Handling Standard module signal. See doc for general rules about signals usage in Python. Signal handlers are callable f(signalnum,stackframe). alarm(time)→ float_delay: previous alarm remaining time - request a new SIGALRM in time seconds - cancel previous one - time≠0 (Unix) alarm(0)→ float_delay: previous alarm remaining time - cancel previous alarm (Unix) getsignal(signalnum)→ fct: current signal handler or SIG_IGN or SIG_DFL or None (handler not installed from Python) pause() ➤ sleep process until a signal is received (Unix) signal(signalnum,handler)→ fct: previous handler for signal (as getsignal) - install new handler (maybe SIG_IGN or SIG_DFL too) - only callable in main thread Following signal constants are defined : SIG_DFL → 0: default signal handler function SIG_IGN → 1: ignore signal handler function NSIG → int: highest signal number +1 Module also defines signal numbers (Posix examples - runtime definition is platform dependant) : SIGHUP terminal or control processus disconnection SIGINT keyboard interrupt SIGQUIT quit request from keyboard SIGILL illegal instruction SIGABRT abort stop signal SIGFPE floating point error SIGKILL the KILL signal SIGSEGV invalid memory reference SIGPIPE pipe write without reader SIGALRM alarm timer elapsed SIGTERM termination signal SIGUSR1 user signal 1 SIGUSR2 user signal 2 SIGCHLD terminated/stopped child SIGCONT continue process (if stopped) SIGSTOP stop process SIGTSTP stop request from keyboard SIGTTIN read on tty while in background SIGTTOU write on tty while in background … → see your platform documentation (man 7 signal on Linux). Functions to send signals are in os module : kill(pid,sig) ➤ kill process pid with signal sig (Unix) killpg(pgid,sig) ➤ kill process group pgid with signal sig (Unix) Simple External Process Control Use standard module subprocess. It wraps external process creation and control in Popen objects. Child process exceptions raised before execution are re-raised in parent process, exceptions will have child_traceback attribute (string). Note : subprocess tools will never call /bin/sh implicitly. PIPE → -1: constant value used for Popen stdin stdout stderr params call(*args,**kwargs)→ int: run command with arguments, wait for completion, return retcode - convenient wrapper around Popen object Use Popen objects as process control tools : p = Popen(args,bufsize=0,executable=None,stdin=None,stdout=None, stderr=None,preexec_fn=None,close_fds=False,shell=False,cwd=None, env=None,universal_newlines=False,startupinfo=None,creationflags=0) args is a string/list of strings ["command","arg1","arg2",…] bufsize like for file/open functions executable can be used to provide command in place of args[0] stdin, stdout and stderr can be PIPE to capture file and communicate with subprocess preexec_fn is called just before child process execution close_fds bool force subprocess inherited files to be closed, except 0 1 and 2 shell bool force execution of command throught the shell cwd string specify working directory to set for subprocess start env dictionnary specify environment variables for subprocess universal_newlines translate all newlines to \n (like U mode for files) startupinfo and creationflags are optional informations for process creation under Windows p.poll()→ int/None: check child process termination, return returncode attribute p.wait()→ int: wait for child process to terminate, return returncode attribute p.communicate(input=None)→ (stdout,stderr): send data (input string)to stdin, read data from stdout/stderr until end-of-file, wait process to terminate, return read values - data read is buffered in memory p.stdin → file/None: standard input from chil process if captured p.stdout → file/None: standard output from chil process if captured p.stderr → file/None: error output from chil process if captured → int: process ID of child process p.returncode → int/None: child process return code (None if not terminated) - on Unix -N for subprocess terminated by signal N Use subprocess module when possible (cleaner, simpler interface, see docs for examples). See also external module pexpect. Advanced External Process Control See following functions from os module. execl(path,[arg[,…]]) execle(path,[arg[,…]],env) execlp(file,[arg[,…]]) execlpe(file,[arg[,…]],env) execv(path,args) execve(path,args,env) execvp(file,args) execvpe(file,args,env) With exec… new program replace current process (fct don't return). 'p' versions use PATH to locate executable file. 'e' versions use a dict env to setup new program environment. 'l' versions use a positioned arg, 'v' versions use list of variable args. spawnl(mode,path,[arg[,…]])→ int spawnle(mode,path,[arg[,…]],env) → int spawnlp(mode,file,[arg[,…]])→ int spawnlpe(mode,file,[arg[,…]],env) → int spawnv(mode,path,args) → int spawnve(mode,path,args,env) → int spawnvp(mode,file,args) → int spawnvpe(mode,file,args,env) → int With spawn… new process is created. 'lpev' versions like for exec…. If mode is P_NOWAIT or P_NOWAIT0, return child pid (Unix) or process handle (Windows). If mode is P_WAIT, wait child termination and return its exit code (>0) or its killing signal (<0). On Windows mode can be, P_DETACH (same as P_NOWAIT but new process detached from calling process console) or P_OVERLAY (current process is replaced). fork()→ pid: fork a child process, return 0 in child, child pid in parent (Unix) forkpty()→ (int{2}): (pid,fd): fork using new pseudo-terminal for child - pid is 0 in child, child pid in parent - fd pseudo-terminal master end (Unix) startfile(path) ➤ open file path as if double-clicked in explorer (Windows) system(cmd)→ value: execute string cmd in subshell - generally return (pid/status) (Unix) or status (Windows) wait()→ (int{2}): (pid,status) wait completion of a child process (Unix) - status=0xZZTT where ZZ=exit code, TT=signal num waitpid(pid,options)→ (int{2}): (pid,status) (Unix): pid>0 wait for specific process, pid=0 wait for any child in process group, pid=-1 wait for any child of current process, pid<-1 wait for any process in process group -pid option in WNOHANG, WCONTINUED, WUNTRACED status=0xZZTT where ZZ=exit code, TT=signal num waitpid(pid,options)→ (int{2}): (pid,status) (Windows): pid is any process handle (>0) - option ignored - status=0xZZ00 where ZZ=exit code Status informations extraction WCOREDUMP(status)→ bool: test process generated core-dump (Unix) WIFCONTINUED(status)→ bool: test process continued from a job control stop (Unix) WIFSTOPPED(status)→ bool: test process stopped (Unix) WIFSIGNALED(status)→ bool: test exited on signal (Unix) WIFEXITED(status)→ bool: test process exited via exit(2) system call (Unix) WEXITSTATUS(status)→ int: if exited via exit(2), return exit parameter (Unix) WSTOPSIG(status)→ int: signal having stopped process (Unix) WTERMSIG(status)→ int: signal having exited process (Unix) 14a 14b 14c Pipes On Process Three functions available in popen2 module (and in os module where stdin/stdout return values are inverted). popen2(cmd[,bufsize[,mode]])→ (file{2}): (stdout,stdin): execute cmd as sub-process popen3(cmd[,bufsize[,mode]])→ (file{3}): (stdout,stdin,stderr): execute cmd as sub-process popen4(cmd[,bufsize[,mode]])→ (file{2}): stdout_stderr,stdin): execute cmd as sub-process Where bufsize is buffer size for I/O pipes, and mode is 'b' (binary streams) or 't' (text streams, default). Param cmd is a string passed to os.system - on Unix it can be a sequence of strings passed directly to the program without shell intervention. On Unix, popen2 module also defines Popen3 class (used in popen2 and popen3 functions) and Popen4 class (used in popen4 function) : Popen3(cmd[,capturestderr[,bufsize]])→ Popen3: cmd: str shell command, captudestderr: bool (default False) Popen4(cmd[,bufsize])→ Popen4 Popen3 and Popen4 objects have following attributes : p.poll()→ int: child return code or -1 if child not terminated p.wait()→ int: child return code p.fromchild → file: output from child (stdout and stderr for Popen4) p.tochild → file: input to child p.childerr → file: error output from child if requested else None (None for Popen4) → int: child process pid See also module commands (Unix). XML PROCESSING Several modules to process XML are available. Some with standard SAX and DOM interfaces, others with more Pythonic interfaces. See also third party PyXML extension package. SAX - Event-driven Base functions in xml.sax module. make_parser([parser_list]) → XMLReader: built from first parser available parse(filename_or_stream,content_handler[,error_handler]) ➤ parse document using first parser available parseString(string,content_handler[,error_handler]) ➤ parse string using first parser available XMLReader Interface Defined in xml.sax.xmlreader. p = xml.sax.make_parser() → XMLReader object p.parse(source) ➤ completly parse source - source is filename or URL or file- like or InputSource- input byte streams (not character streams) p.getContentHandler() → ContentHandler: current one p.setContentHandler(handler) ➤ set current content handler p.getDTDHandler() → DTDHandler: current one p.setDTDHandler(handler) ➤ set current DTD handler p.getEntityResolver() → EntityResolver: current one p.setEntityResolver(handler) ➤ set current entity resolver p.getErrorHandler() → ErrorHandler: current one p.setErrorHandler(handler) ➤ set current error handler p.setLocale(locale) ➤ set locale for errors and warnings p.getFeature(featurename) → current settings for feature1 p.setFeature(featurename,value) ➤ set feature to value p.getProperty(propertyname) → current settings for property2 p.setProperty(propertyname,value) ➤ set property to value There is also an IncrementalParser subclass interface with : p.feed(data) ➤ process a chunk of data p.close() ➤ assume end of document, check well-formedness, cleanup p.reset() ➤ after close, prepare new parsing 1 Feature names in xml.sax.handler as feature_xxx. 2 Property names in xml.sax.handler as property_xxx. InputSource Interface Provide source of data for parser. isrc.setPublicId(id) ➤ set public identifier isrc.getPublicId() → unicode: public identifier isrc.setSystemId(id) ➤ set system identifier isrc.getSystemId() → unicode: system identifier isrc.setEncoding(encoding) ➤ set encoding - must be a string acceptable for an XML encoding declaration - ignored if InputSource contains character stream isrc.getEncoding() → str/None (if unknown) isrc.setByteStream(bytefile) ➤ set input byte stream - ignored if InputSource contains character stream isrc.getByteStream() → byte stream isrc.setCharacterStream(charfile) ➤ set character (Unicode) stream isrc.getCharacterStream() → character stream Locator Interface Instances of Locator provide these methods: loc.getColumnNumber() → int: column number where current event ends loc.getLineNumber() → int: line number where current event ends loc.getPublicId() → str: public identifier of current event loc.getSystemId() → str: system identifier of current event Attributes Interface Also implement parts mapping protocol (copy(), get(), has_key(), items(), keys(), and values()). ai.getLength() → int: number of attributes ai.getNames() → [unicode]: names of attributes ai.getType(name)→ type of attribute name - normally 'CDATA' ai.getValue(name)→ unicode: value of attribute name AttributesNS Interface Also implement Attributes interface. ansi.getValueByQName(name)→ unicode: value of attribute qualified name ansi.getNameByQName(name)→ (unicode{2}): (namespace, localname) for qualified name ansi.getQNameByName(namepair)→ unicode: qualified name for (namespace, localname) ansi.getQNames()→ [unicode]: qualified names of all attributes ContentHandler Interface Defined in xml.sax.handler. Its methods are handlers called when parser find XML structures. ch = MyContentHandler() → ContentHandler subclass object ch.setDocumentLocator(locator) ➤ set locator for origin of document events ch.startDocument() ➤ beginning of document ch.endDocument() ➤ end of document ch.startPrefixMapping(prefix,uri) ➤ begin of a prefix-URI namespace mapping - see doc ch.endPrefixMapping(prefix) ➤ end of a prefix-URI namespace mapping ch.startElement(name,attrs) ➤ start of an element - non-namespace mode - attrs has an Attributes interface (may be reused - copy data) ch.endElement(name) ➤ end of an element - non-namespace mode ch.startElementNS(name,qname,attrs) ➤ start of an element - namespace mode - name is (uri,localname) - qname is raw XML name - attrs has an AttributesNS interface (may be reused - copy data) - qname may be None (upon feature_namespace_prefixes) ch.endElementNS(name,qname) ➤ end of an element - namespace mode ch.characters(content) ➤ character data - content is str or unicode ch.ignorableWhitespace(whitespace) ➤ whitespaces ch.processingInstruction(target,data) ➤ processing instruction ch.skippedEntity(name) ➤ entity not processed DTDHandler Interface Defined in xml.sax.handler. Its methods are handlers called when parser need DTD relative work. dh = MyDTDHandler() → DTDHandler subclass object dh.notationDecl(name,publicId,systemId) ➤ notation declaration dh.unparsedEntityDecl(name,publicId,systemId,ndata) ➤ unparsed entity declaration EntityResolver Interface Defined in xml.sax.handler. Its methods are handlers called when parser need external entity resolution. er = MyEntityResolver() → EntityResolver interface object er.resolveEntity(publicId,systemId) → str/InputSource: default return systemId Exceptions Defined in xml.sax module. SAXException(msg[,exception]) SAXParseException(msg,exception,locator) ― invalid XML SAXNotRecognizedException(msg[,exception]) SAXNotSupportedException(msg[,exception]) ErrorHandler Interface Defined in xml.sax.handler. Its methods are handlers called when parser detect an error. Their exception parameters get SAXParseException objects. eh = MyErroHandler() → ErrorHandler interface object eh.error(exception) ➤ recovererable error - parsing will continue if method return eh.fatalError(exception) ➤ unrecoverable error - parsing must stop eh.warning(exception) ➤ minor warning - parsing will continue if method return SAX Utilities Defined in xml.sax.saxutils. escape(data[,entities]) → str: & < > escaped - escape other entities replacing mapping strings (keys) by corresponding identifiers unescape(data[,entities]) → str: & < > unescaped - unescape other entities replacing mapping identifiers (keys) by corresponding strings quoteattr(data[,entities]) → str: as escape + quote string to be used as attribute value prepare_input_source(source[,base]) → InputSource: source is string, file-like, or InputSource - base is an URL string - return InputSource for parser Class XMLGenerator is a ContentHandler writing SAX events into an XML document (ie. reproduce original document). XMLGenerator([out[,encoding]]) → content handler: out file-like, deault to sys.stdout - encoding default to 'iso-8859-1' Class XMLFilterBase is a default pass-throught events, can be subclassed to modify events on-fly before their processing by application handlers. XMLFilterBase(base) → events filter Features & Properties Defined in xml.sax.handler. Dont give their value, but their meaning. feature_namespaces1 → True: perform namespace processing. False: no namespace processing (so no namespace prefixes). feature_namespace_prefixes1 → True: report original prefixed names and attributes used for namespace declarations. feature_string_interning1 → True: intern all names (elements, prefixes, attributes, namespace URIs, local names). feature_validation1 → True: report all validation errors. feature_external_ges1 → True: include all external general (text) entities. feature_external_pes1 → True: include all external parameter entities, including the external DTD subset. 15a 15b 15c all_features → list of all features property_lexical_handler → optional extension handler for lexical events (like comments). property_declaration_handler → optional extension handler for DTD- related events other than notations and unparsed entities. property_dom_node1 → visited DOM node (if DOM iterator) when parsing, else root DOM node. property_xml_string → literal string source of current event (read only property). all_properties → list of all properties names 1 can only be read during parsing (and modified before). DOM - In-memory Tree Defined in xml.dom. Two function to register/access DOM processors, and some constants. registerDOMImplementation(name,factory) ➤ register DOM implementation factory getDOMImplementation([name[,features]]) → DOM implementation - name may be None - may found name in env. var PYTHON_DOM - features is [(featurename,version),…] EMPTY_NAMESPACE → no namespace associated with a node XML_NAMESPACE → xml prefix namespace XMLNS_NAMESPACE → namespace URI for namespace declarations - DOM level 2 specification definition XHTML_NAMESPACE → URI of XHTML namespace (XHTML 1.0) DOMImplementation impl.hasFeature(feature,version) → bool: test for supported feature in an implementation Node Defined in xml.dom, class Node is parent of XML components nodes classes. o.nodeType → int: (ro) in ELEMENT_NODE, ATTRIBUTE_NODE, TEXT_NODE, CDATA_SECTION_NODE, ENTITY_NODE, PROCESSING_INSTRUCTION_NODE, COMMENT_NODE, DOCUMENT_NODE, DOCUMENT_TYPE_NODE, NOTATION_NODE o.parentNode → Node/None: (ro) - None for Attr nodes o.attributes → NamedNodeMap/None: attribute objects for elements, else None o.previousSibling → Node/None: (ro) previous node in parent's children o.nextSibling → Node/None: (ro) next node in parent's children o.childNodes → [Node]: (ro) list of subnodes o.firstChild → Node/None: (ro) first subnode o.lastChild → Node/None: (ro) last subnode o.localName → unicode/None: (ro) element name without namespace prefix o.prefix → unicode/None: (ro) element namespace prefix - may be empty string or None o.namespaceURI → unicode/None: (ro) URI associated to element namespace o.nodeName → unicode/None: (ro) usage specified in subclasses o.nodeValue → unicode/None: (ro) usage specified in subclasses o.hasAttributes() → bool: test any attribute existence o.hasChildNodes() → bool: test any subnode existence o.isSameNode(other) → bool: test other refers same node o.appendChild(newChild) → new Child: add new child node at end of subnodes - return new child o.insertBefore(newChild,refChild) → new Child: add new child node before an existing subnode - at end of subnodes if refChild is None - return new child o.removeChild(oldChild) → oldChild: remove a subnode, return it - when no longer used, must call oldChild.unlink() o.replaceChild(newChild,oldChild) ➤ replace existing subnode with a new one o.normalize() ➤ join adjacent text nodes o.cloneNode(deep) → Node: if deep, clone subnodes too - return clone NodeList A sequence of nodes, usable as a Python sequence (maybe modifiable upon implementation). o.length → int: number of nodes in the sequence o.item(i) → Node/None: ith item in the list DocumentType Subclass of Node. o.nodeType → DOCUMENT_TYPE_NODE o.publicId → unicode/None: public identifier for external subset of DTD o.systemId → unicode/None: system identifier URI for external subset of DTD o.internalSubset → unicode/None: complete internal subset from the document - without brackets → unicode/None: name of root element (as given in DOCTYPE) o.entities → NamedNodeMap/None: definition of external entities o.notations → NamedNodeMap/None: definition of notations Document Subclass of Node. o.nodeType → DOCUMENT_NODE o.documentElement → Element: root element of the document o.createElement(tagName)→ Element: new1 element node o.createElementNS(namespaceURI,tagName)→ Element: new1 element node with namespace - tagName may have prefix o.createTextNode(data) → Element: new1 text node containing data o.createComment(data) → Element: new1 comment node containing data o.createProcessingInstruction(target,data) → Element: new1 processing instruction node containing target and data o.createAttribute(name) → Element: new1 attribute node o.createAttributeNS(namespaceURI,qualifiedName) → Element: new1 attribute node with namespace - tagName may have prefix o.getElementsByTagName(tagName) → NodeList: search for all descendants (deep search) having type tagName o.getElementsByTagNameNS(namespaceURI,localName) → NodeList: search for all descendants (deep search) having namespaceURI and localName (part after prefix) 1 New nodes are standalone - you must insert/associate them in/to document parts. Element Subclass of Node. o.nodeType → ELEMENT_NODE o.tagName → unicode: element type name - with namespace may contain colons o.getElementsByTagName(tagName) → NodeList: search for all descendants (deep search) having type tagName o.getElementsByTagNameNS(namespaceURI,localName) → NodeList: search for all descendants (deep search) having namespaceURI and localName (part after prefix) o.getAttribute(attname)→ unicode: attribute value o.getAttributeNode(attrname)→ Attr: attribute node o.getAttributeNS(namespaceURI,localName)→ unicode: attribute value o.getAttributeNodeNS(namespaceURI,localName)→ Attr: attribute node o.removeAttribute(attname) ➤ remove attribute by name - ignore missing attribute o.removeAttributeNode(oldAttr)→ Attr: remove and return oldAttr o.removeAttributeNS(namespaceURI,localName) ➤ remove attribute by namespace URI and name - ignore missing attribute o.setAttribute(attname,value) ➤ set attribute string value o.setAttributeNode(newAttr)→ Attr: set attribute from a new Attr node - return old one o.setAttributeNodeNS(newAttr)→ Attr: set attribute from a new Attr node with namespace URI and local name - return old one o.setAttributeNS(namespaceURI,qname,value)→ Attr: set attribute string value from a namespaceURI and qname (whole attribute name) - return old one Attr Subclass of Node. o.nodeType → ATTRIBUTE_NODE → unicode: (ro) attribute full name - may have colons o.localName → unicode: (ro) attribute name - part after colons o.prefix → unicode: (ro) attribute prefix - part before colons - may be empty NamedNodeMap A mapping of nodes - experimentally usable as a Python mapping. o.length → int: length of attributes list o.item(index) → Attr: attribute at index - arbitrary but consistent order Comment Subclass of Node. Cannot have subnode. o.nodeType → COMMENT_NODE → unicode: content of the comment, without Text Subclasses of Node. Cannot have subnode. Text part in an element. o.nodeType → TEXT_NODE → unicode: text content CDATASection Subclasses of Node. Cannot have subnode. CDATA section in a document, may have multiple CDATASection nodes for one CDATA. o.nodeType → CDATA_SECTION_NODE → unicode: CDATA content ProcessingInstruction Subclasses of Node. Cannot have subnode. Represents a processing instruction in the XML document; this inherits from the Node interface and cannot have child nodes. o.nodeType → PROCESSING_INSTRUCTION_NODE → unicode: (ro) processing instruction content up to first whitespace → unicode: (ro) processing instruction content after first whitespace Exceptions Python map DOM error codes to exceptions. DOM codes constants Exception DOMSTRING_SIZE_ERR DomstringSizeErr HIERARCHY_REQUEST_ERR HierarchyRequestErr INDEX_SIZE_ERR IndexSizeErr INUSE_ATTRIBUTE_ERR InuseAttributeErr INVALID_ACCESS_ERR InvalidAccessErr INVALID_CHARACTER_ERR InvalidCharacterErr INVALID_MODIFICATION_ERR InvalidModificationErr INVALID_STATE_ERR InvalidStateErr NAMESPACE_ERR NamespaceErr NOT_FOUND_ERR NotFoundErr NOT_SUPPORTED_ERR NotSupportedErr NO_DATA_ALLOWED_ERR NoDataAllowedErr NO_MODIFICATION_ALLOWED_ERR NoModificationAllowedErr SYNTAX_ERR SyntaxErr WRONG_DOCUMENT_ERR WrongDocumentErr exception.code → int: DOM code corresponding to exception exception.msg → string: message for exception DOMException DomstringSizeErr ― implementation limit reach HierarchyRequestErr ― insert at wrong place IndexSizeErr ― index range error InuseAttributeErr ― Attr node already used in tree InvalidAccessErr ― param/operation unsupported by object InvalidCharacterErr ― character invalid in the context InvalidModificationErr ― can't modify node type InvalidStateErr ― try to use an undefined/unusable object 16a 16b 16c NamespaceErr ― change forbidden in namespace context NotFoundErr ― node don't exist in referenced context NotSupportedErr ― operation/type unsupported by implementation NoDataAllowedErr ― no data for this node NoModificationAllowedErr ― can't modify object SyntaxErr ― invalide/illegal string WrongDocumentErr ― impl. can't migrate nodes between docs DATABASES See wiki for a list of database interface modules. Some interfaces are for external DB engines (MySQL, PostgreSQL, BerkeleyDB, SQLite, Metakit…), other for pure Python DB engines (gadfly, ZODB, KirkyBase, Buzhug…). Generic access to DBM-style DBs Standard module anydbm is a front-end to some available DB modules : dbhash (→bsddb→Berkeley DB), gdbm (→GNU dbm), dbm (→unix dbm) and the slow portable fallback dumbdbm. Data stored in DBM-style files are accessed via a dictionary-like interface where keys and values must be str. open(filename[,flag[,mode]]) → dictionary-like object: flag in 'r' (read- default), 'w' (write), 'c' (create if doesn't exist), 'n' (create new empty) - mode is unix mode flags for creation error → tuple of exception classes from DB modules (anydbm.error,…) Uses module whichdb to identify right DB module for existing file. For new files, use first available DB module in the order of the list. This is used by shelve module (see Persistence, p12). DB modules can have specific functions related to their backend, see docs. Standard DB API for SQL databases Generally modules for SQL databases use the Standard Python Database API v2 (defined in PEP249). API Informations apilevel → str: currently '1.0' or '2.0' - '1.0' if undefined threadsafety → int: level of thread safety # share module share connections share cursors 0 no no no 1 yes no no 2 yes yes no 3 yes yes yes paramstyle → str: parameter marker for requests value params example 'qmark' Question mark style1 …WHERE name=? 'numeric' Numeric, positional style1 or 2 …WHERE name=:1 'named' Named style2 …WHERE name=:name 'format' ANSI C printf format codes1 …WHERE name=%s 'pyformat Python extended format codes2 …WHERE name=%(name)s 1 Parameters as positional values in a sequence. 2 Parameters as named values in a map. Exceptions (StandardError) Warning ― important warning Error ― a catch all InterfaceError ― problem with interface (not database) DatabaseError DataError ― problem with data processing OperationalError ― problem during database operations IntegrityError InternalError ProgrammingError ― SQL programming related error NotSupportedError Exceptions classes may also be available as Connection objects attributes (optional). Connection connect(dsn[,user[,password[,host[,database]]]])→ Connection object (interface defined as a guideline) - dsn=data source name string cx.errorhandler → fct: (optional) handler for connection errors - errorhandler(connection, cursor/None, errorclass, errorvalue) - default handler fill cx.messages and may raise exceptions cx.messages → [(exception class,exception value)]: (optional) messages received from database for operations with connection cx.close() ➤ terminate connection (may rollback if not commited) cx.commit() ➤ commit pending transactions cx.rollback() ➤ rollback pending transactions (optionnal) cx.cursor()→ new Cursor object Cursor cu.arraysize → int: (RW) number of rows to fetch with fetchmany - default to 1 cu.connection → Connection: (optional) connection used by cursor cu.description → [(name, type_code, display_size, internal_size, precision, scale, null_ok)]/None: describe result columns cu.errorhandler → fct: (optional) handler for connection errors - errorhandler(connection, cursor, errorclass, errorvalue) - default handler fill cx.messages and may raise exceptions - inherited from connection cu.lastrowid → int/None: (optional) row id of last modified column cu.messages → [(exception class,exception value)]: (optional) messages received from database for operations with cursor cu.rowcount → int: number of rows produced/affected by last request - -1 or None if request cant touch rows cu.rownumber → int/None: (optional) 0-based index of the cursor in the result set if available cu.callproc(procname[,parameters])→ (parameters) - (optional) call DB stored procedure - in result out and inout parameters may have been replaced by procedure cu.close()ä close the cursor cu.execute(oper[,params]) ➤ prepare and execute DB request - params1 is a sequence or a mapping (see module paramstyle variable) cu.executemany(oper,params_seq) ➤ like execute, with a sequence of params (for multiple values) cu.fetchone()→ (column_value,…) / None: next row of query result, None when no more data available cu.fetchmany([size])→ [(column_value)]: next set of rows of query result, empty list when no more data available - size default to cu.arraysize cu.fetchall()→ [(column_value)]: all remaining rows of query result, empty list when no more data available→ (column_value) : (optional) next row of query result, raises StopIteration when no more data available cu.nextset() → True/None: (optional) discards results up to next available set cu.scroll(value[,mode]) ➤ (optional) - scroll cursor in current result set - mode is 'relative' (default) or 'absolute'. cu.setinputsizes(sizes) ➤ predefine memory areas for executeXXX operations parameters - sizes=[param_size,…] - param_size=Type Object or int (max length of a string param) - param_size=None for no predefinition cu.setoutputsize(size[,column]) ➤ set column buffer size for fetches of large columns (e.g. LONGs, BLOBs, etc.) by executeXXX - column is index in result - all columns if column not specified cu.__iter__() → Cursor: (optional) object itself 1 Method __getitem__ is used to get values in params, using position or name. Can use tuple or dict… or your own class objects with its __getitem__. If next and __iter__ are defined, cursors are iterable. DB types Constructors Date(year,month,day)→ object to hold a date value Time(hour,minute,second)→ object to hold a time value Timestamp(year,month,day,hour,minute,second)→ object to hold a time stamp value DateFromTicks(ticks)→ object to hold a date value from a given ticks value TimeFromTicks(ticks)→ object to hold a time value from a given ticks value TimestampFromTicks(ticks)→ object to hold a time stamp value from a given ticks value Binary(string)→ object to hold a long binary string value SQL NULL values represented by Python None. DB types Typecodes STRING → string-based column (CHAR) BINARY → long binary column (LONG, RAW, BLOBs) NUMBER → numeric column DATETIME → date/time column ROWID → row ID column (CHAR) BULK Tools Batteries included: pdb (Python debugger), code bench with timeit (p9). A must have: pychecker. Take a look: pylint, psyco, pyrex, pycount, trace2html, depgraph, coverage, pycover, Pyflakes, pyreverse, HAP. Links Docs: FAQ Python: PEPs: (Python Enhancement Proposal) HOWTOs: Cookbook: Dive Into: 17a 17b 17c ©2005-2007 - Laurent Pointal V0.67 — 2007-4-29 License : Creative Commons [by nc sa]. PQRC at Long Python Quick Reference at Original Python reference at



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