Python 2.5 Reference Card (c) 2007 Michael Goerz http://www.physik.fu-berlin.de/~goerz/ Information taken liberally from the python documentation and various other sources. You may freely modify and distribute this document. 1 Variable Types 1.1 Numbers 42 052 0x2A 42L 052L 0x2AL 42 (dec, oct, hex, short/long) 0.2 .8 4. 1.e10 1.0e-7 floating point value z = 5.0 – 2.0J; complex number z = complex(real, imag) complex number z.real; z.imag real and imag part of z True; False constants for boolean values abs(n) absolute value of n divmod(x, y) (x/y, x%y) hex(n) create hex string oct(n) create octal string ord(c) unicode code point of char round(x,n) round x to n decimal places cmp(x,y) xy: 1 coerce(x, y) (x,y), make same type pow(x,y,z) (x**y) % z float("3.14") float from string int("42", base) int from string import math; import cmath more math functions import random; random number generators 1.2 Sequences (lists are mutable, tuples and strings are immutable) s=l=[1, "bla", [1+2J, 1.4], 4] list creation s=t=(1, "bla", [1+2J, 1.4], 4) tuple creation l=list(t); t=tuple(l) list/tuple conversion l=range(1000) list of integers (0-999) s=xrange(1000) immut. xrange-sequence i=iter(s); i.next() iterator from sequence s[2][0] get list element (1+2J) s[-2][-1] get list element (1.4) s1+s1 sequence concat n*s1 repeat s1 n times s[i:j]; s[i:]; s[:j] slicing (i incl., j excl.) s[i:j:k] slice with stride k s[::2]; s[::-1] every 2nd Element / reverse s x in s; x not in s is x a member of s? len(s) number of elements min(s); max(s) min/max l[i:j]=['a','b','c','d'] replace slice l[i:i]=['a','b'] insert before position i l.count(x) number of occurances of x l.index(x) first index of x, or error l.append(x) append x at end of l x=l.pop() pop off last element l.extend(l2) append l2 at end of l l.insert(i,x) instert x at pos. i l.remove(x) delete first x l.reverse() reverse l l.sort(f) sort using f (default f =cmp) zip(s,t,...) [(s[0],t[0],...),..] 1.3 Dictionaries (Mappings) d={'x':42, 'y':3.14, 'z':7} dict creation d['x'] get entry for 'x' len(d) number of keys del(d['x']) delete entry from dict d.copy() create shallow copy d.has_key(k) does key exist? d.items() list of all items d.keys() list of all keys d.values() list of all values i=d.iteritems(); i.next() iterator over items i=d.iterkeys(); i.next() iterator over keys i=d.itervalues(); i.next() iterator over values d.get(k,x) get entry for k, or return x d.clear() remove all items d.setdefault(k,x) return d[k] or set d[k]=x d.popitem() return and delete an item 1.4 Sets s=set(s); fs=frozenset(s) create set fs.issubset(t); s<=t all s in t? fs.issuperset(t); s>=t all t in s? fs.union(t); s|t all elements from s and t fs.intersection(t); s&t elements both in s and t fs.difference(t); s-t all s not in t fs.symmetric_difference(t);s^t all either s or t fs.copy() shallow copy of s s.update(t); s|=t add elements of t s.intersection_update(t); s&=t keep only what is also in t s.difference_update(t); s-=t remove elements of t s.symmetric_differ...(t); s^=t keep only symm. difference s.add(x) add x to fs s.remove(x); fs.discard(x); remove x (/ with exception) s.pop(); return and remove any elem. s.clear(); remove all elements 1.5 Strings and Regular Expressions "bla"; 'hello "world"' string (of bytes) """bla""", '''bla''' triple quotes for multiline \ \\ \0 cont., backslash, null char \N{id} \uhhhh \Uhhhhhhhh unicode char \xhh \ooo hex, octal byte u"Ünic\u00F8de"; u"\xF8" unicode string (of characters) r"C:\new\text.dat"; ur"\\Ü" raw string (unicode) str(3.14); str(42) string conversion "%s-%s-%s" % (42,3.14,[1,2,3]) string formatting '\t'.join(seq) join sequences with separator s.decode('utf-8') latin-1 string to unicode string u.encode('utf-8') unicode string to utf-8 string chr(i), unichr(i) char from code point str(x) string from number/object Other String Methods: search and replace: find(s,b,e), rfind(s,b,e), index(s,b,e), rindex(s,b,e), count(s,b,e), endswith(s,b,e), startswith(s,b,e), replace(o,n,m) formatting: capitalize, lower, upper, swapcase, title splitting: partition(s), rpartition(s), split(s,m), rsplit(s,m), splitlines(ke) padding: center(w,c), ljust(w,c), lstrip(cs), rjust(w,c), rstrip(cs), strip(cs), zfill(w), expandtabs(ts) checking: isalnum, isalpha, isdigit, islower, isspace, istitle, isupper String Constants: import string digits, hexdigits, letters, lowercase, octdigits, printable, punctuation, uppercase, whitespace Regexes: import re r=re.compile(r'rx',re.ILMSUX) comile 'rx' as regex (?P...) named group m=r.match(s,b,e) full match re.match(r'(?iLmsux)rx',s) direct regex usage m=r.search(s,b,e) partial match l=r.split(s,ms) split and return list l=r.findall(string) list of all matched groups s=r.sub(s,r,c) replace c counts of s with r (s,n)=r.subn(s,r,c) n is number of replacements s=re.escape(s) escape all non-alphanumerics m.start(g);m.span(g);m.end(g) group-match delimiters m.expand(s) replace \1 etc. with matches m.group(g); m.group("name") matched group no. g m.groups() list of groups m.groupdict() dict of named groups 2 Basic Syntax if expr: statements elif expr: statements else: statements conditional if a is b : ... object identity if a == 1 value identity while expr: statements else: statements while loop run else on normal exit while True: ... if cond: break do... while equivalent for target in iter: statements else: statements for loop for key,value in d.items():... multiple identifiers break, continue end loop / jump to next print "hello world", print without newline [ expr for x in seq lc ] lc = for x in seq / if expr list comprehension with lc-clauses pass empty statement def f(params): statements function definition def f(x, y=0): return x+y optional parameter def f(*a1, **a2): statements additional list of unnamed, dict of named paramters def f(): f.variable = 1 ... function attribute return expression return from function yield expression make function a generator f(1,1), f(2), f(y=3, x=4) function calls global v bind to global variable def make_adder_2(a): def add(b): return a+b return add closure lambda x: x+a lambda expression compile(string,filename,kind) compile string into code object eval(expr,globals,locals) evaluate expression exec code in gldict, lcdict compile and execute code execfile(file,globals,locals) execute file raw_input(prompt) input from stdin input(prompt) input and evaluate 3 Object Orientation and Modules import module as alias import module from module import name1,name2 load attr. into own namespace from __future__ import * activate all new features reload module reinitialize module module.__all__ exported attributes module.__name__ module name / "__main__" module.__dict__ module namespace __import__("name",glb,loc,fl) import module by name class name (superclass,...): data = value def method(self,...): ... def __init__(self, x): Super.__init__(self) self.member = x def __del__(self): ... class definition shared class data methods constructor call superclass constructor per-instance data destructor __str__, __len__, __cmp__,__ some operator overloaders __iter__(self): return self use next method for iterator __call__ call interceptor __dict__ instance-attribute dictionary __getattr__(self, name), get an unknown attribute __setattr__(self, name, value) set any attribute callable(object) 1 if callable, 0 otherwise delattr(object, "name") delete name-attr. from object del(object) unreference object/var dir(object) list of attr. assoc. with object getattr(object, "name", def) get name-attr. from object hasattr(object, "name") check if object has attr. hash(object) return hash for object id(object) unique integer (mem address) isinstance(object, classOrType) check for type issubclass(class1, class2) class2 subclass of class1? iter(object, sentinel) return iterator for object locals() dict of local vars of caller repr(object), str(object) return string-representation vars(object) return __dict__ None the NULL object if __name__ == "__main__": make modul executable 4 Exception Handling try: ... except ExceptionName: except (Ex1, ...), data: print data raise else: ... finally: ... Try-block catch exception multiple, with data exception handling pass up (re-raise) exception if no exception occurred in any case assert expression debug assertion class MyExcept(Exception): ... define user exception raise MyExcept , data raise user exception 5 System Interaction sys.path module search path sys.platform operating system sys.stdout, stdin, stderr standard input/output/error sys.argv[1:] command line parameters os.system(cmd) system call os.startfile(f) open file with assoc. program os.popen(cmd, r|w, bufsize) open pipe (file object) os.popen2(cmd, bufsize, b|t) (stdin, stdout) fileobjects os.popen3(cmd, bufsize, b|t) (stdin, stdout,stderr) os.environ['VAR']; os.putenv[] read/write environment vars glob.glob('*.txt') wildcard search Filesystem Operations os module: access, chdir, chmod, chroot, getcwd, getenv, listdir, mkdir, remove, unlink, removedirs, rename, rmdir, pipe, ... shutil module: copy, copy2, copyfile, copyfileobj, copymode, copystat, copytree, rmtree os.path module: abspath, altsep, basename, commonprefix, curdir, defpath, dirname, exists, expanduser, expandvar, extsep, get[acm]time, getsize, isabs, isdir, isfile, islink, ismout, join, lexists, normcase, normpath, pardir, pathsep, realpath, samefile, sameopenfile, samestat, sep, split, splitdrive, splitext, stat, walk command line argument parsing: restlist, opts = \ getopt.getopt(sys.argv[l:],\ "s:oh",\ ["spam=", "other", "help"]) for o, a in opts: if o in ("-s", "--lol"): spam = a if o in ("-h", "--help"): show_help() 6 Input/Output f=codecs.open(if,"rb","utf-8") open file with encoding file = open(infilename, "wb") open file without encoding codecs.EncodedFile(...) wrap file into encoding r, w, a, r+ read, write, append, random rb, wb, ab, r+b modes without eol conversion file.read(N) N bytes ( entire file if no N ) file.readline() the next linestring file.readlines() list of linestring file.write(string) write string to file file.writelines(list) write list of linestrings file.close() close file file.tell() current file position file.seek(offset, whence) jump to file position os.truncate(size) limit output to size os.tmpfile() open anon temporary file pickle.dump(x, file) make object persistent x = pickle.load(file) load object from file 7 Standard Library (almost complete) String Services: string, re, struct, difflib, StringIO, cStringIO, textwrap, codecs, unicodedata, stringprep, fpformat File/Directory Access: os.path, fileinput, stat, statvfs, filecmp, tempfile, glob, fnmatch, linecache, shutil, dircache Generic OS services: os, time, optparse, getopt, logging, getpass, curses, platform, errno, ctypes Optional OS services: select, thread, threading, dummy_thread, dummy_threading, mmap, readline, rlcompleter Data Types: datetime, calendar, collections, heapq, bisect, array, sets, sched, mutex, Queue, weakref, UserDict, UserList, UserString, types, new, copy, pprint, repr Numeric and Math Modules: math, cmath, decimal, random, itertools, functools, operator Internet Data Handling: email, mailcap, mailbox, mhlib, mimetools, mimetypes, MimeWriter, mimify, multifile, rfc822, base64, binhex, binascii, quopri, uu Structured Markup Processing Tools: HTMLParser, sgmllib, htmllib, htmlentitydefs, xml.parsers.expat, xml.dom.*, xml.sax.*, xml.etree.ElementTree File Formats: csv, ConfigParser, robotparser, netrc, xdrlib Crypto Services: hashlib, hmac, md5, sha Compression: zlib, gzip, bz2, zipfile, tarfile Persistence: pickle, cPickle, copy_reg, shelve, marshal, anydbm, whichdb, dbm, gdbm, dbhash, bsddb, dumbdbm, sqlite3 Unix specific: posix, pwd, spwd, grp, crypt, dl, termios, tty, pty, fcntl, posixfile, resource, nis, syslog, commands IPC/Networking: subprocess, socket, signal, popen2, asyncore, asynchat Internet: webbrowser, cgi, scitb, wsgiref, urllib, httplib, ftplib, imaplib, nntplib, ...lib, smtpd, uuid, urlparse, SocketServer, ...Server,, cookielib, Cookie, xmlrpclib Multimedia: audioop, imageop, aifc, sunau, wave, chunk, colorsys, rgbimg, imghdr, sndhdr, ossaudiodev Tk: Tkinter, Tix, ScrolledText, turtle Internationalization: gettext, locale Program Frameworks: cmd, shlex Development: pydoc, doctest, unittest, test Runtime: sys, warnings, contextlib, atexit, traceback, qc, inspect, site, user, fpectl Custom Interpreters: code, codeop Restricted Execution: rexec, Bastion Importing: imp, zipimport, pkgutil, modulefinder, runpy Language: parser, symbol, token, keyword, tokenize, tabnanny, pyclbr, py_compile, compileall, dis, pickletools, distutils Windows: msilib, msvcrt, _winreq, winsound Misc: formatter