Python 2.7 Quick Reference Sheet

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贡献于2015-02-05

字数:0 关键词: Python开发 Python

Python 2.7 Quick Reference Sheet ver 2.01 ʹ 110105 (sjd) Interactive Help in Python Shell help() Invoke interactive help help(m) Display help for module m help(f) Display help for function f dir(m) Display names in module m Small Operator Precedence Table func_name(args, ͙) Function call x[index : index] Slicing x[index] Indexing x.attribute Attribute reference ** Exponentiation *, /, % Multiply, divide, mod +, - Add, subtract >, <, <=, >=, !=, == Comparison in, not in Membership tests not, and, or Boolean operators NOT, AND, OR Module Import import module_name from module_name import name , ͙ from module_name import * Common Data Types Type Description Literal Ex int long float complex bool str tuple list dict 32-bit Integer Integer > 32 bits Floating point number Complex number Boolean Character sequence Immutable sequence Mutable sequence Mapping 3, -4 101L 3.0, -6.55 1.2J True, False ͞Python͟ (2, 4, 7) [2, x, 3.1] { x:2, y:5 } Common Syntax Structures Assignment Statement var = exp Console Input/Output var = input( [prompt] ) var = raw_input( [prompt] ) print exp[,] ͙ Selection if (boolean_exp): stmt ͙ [elif (boolean_exp): stmt ͙] ͙ [else: stmt ͙] Repetition while (boolean_exp): stmt ͙ Traversal for var in traversable_object: stmt ͙ Function Definition def function_name( parmameters ): stmt ͙ Function Call function_name( arguments ) Class Definition class Class_name [ (super_class) ]: [ class variables ] def method_name( self, parameters ): stmt Object Instantiation obj_ref = Class_name( arguments ) Method Invocation obj_ref.method_name( arguments ) Exception Handling try: stmt ͙ except [exception_type] [, var]: stmt ͙ Common Built-in Functions Function Returns abs(x) Absolute value of x dict() Empty dictionary, eg: d = dict() float(x) int or string x as float id(obj) memory addr of obj int (x) float or string x as int len(s) Number of items in sequence s list() Empty list, eg: m = list() max(s) Maximum value of items in s min(s) Minimum value of items in s open(f) Open filename f for input ord(c) ASCII code of c pow(x,y) x ** y range(x) A list of x ints 0 to x - 1 round(x,n) float x rounded to n places str(obj) str representation of obj sum(s) Sum of numeric sequence s tuple(items) tuple of items type(obj) Data type of obj Common Math Module Functions Function Returns (all float) ceil(x) Smallest whole nbr >= x cos(x) Cosine of x radians degrees(x) x radians in degrees radians(x) x degrees in radians exp(x) e ** x floor(x) Largest whole nbr <= x hypot(x, y) sqrt(x * x + y * y) log(x [, base]) Log of x to base or natural log if base not given pow(x, y) x ** y sin(x) Sine of x radians sqrt(x) Positive square root of x tan(x) Tangent of x radians pi Math constant pi to 15 sig figs e Math constant e to 15 sig figs Common String Methods S.method() Returns (str unless noted) capitalize S with first char uppercase center(w) S centered in str w chars wide count(sub) int nbr of non-overlapping occurrences of sub in S find(sub) int index of first occurrence of sub in S or -1 if not found isdigit() bool True if S is all digit chars, False otherwise islower() isupper() bool True if S is all lower/upper case chars, False otherwise join(seq) All items in seq concatenated into a str, delimited by S lower() upper() Lower/upper case copy of S lstrip() rstrip() Copy of S with leading/ trailing whitespace removed, or both split([sep]) List of tokens in S, delimited by sep; if sep not given, delimiter is any whitespace Formatting Numbers as Strings Syntax: ͞format_spec͟ % numeric_exp format_spec syntax: % width.precision type x width (optional): align in number of colums specified; negative to left-align, precede with 0 to zero-fill x precision (optional): show specified digits of precision for floats; 6 is default x type (required): d (decimal int), f (float), s (string), e (float ʹ exponential notation) x Examples for x = 123, y = 456.789 ͞йϲĚ͟ % x -> . . . 123 ͞йϬϲĚ͟ % x -> 000123 ͞%8.2f % y -> . . 456.79 ͞ϴ͘ϮĞ͟йLJ-> 4.57e+02 ͞-8s͟й͞,ĞůůŽ͟-> Hello . . . Common List Methods L.method() Result/Returns append(obj) Append obj to end of L count(obj) Returns int nbr of occurrences of obj in L index(obj) Returns index of first occurrence of obj in L; raises ValueError if obj not in L pop([index]) Returns item at specified index or item at end of L if index not given; raises IndexError if L is empty or index is out of range remove(obj) Removes first occurrence of obj from L; raises ValueError if obj is not in L reverse() Reverses L in place sort() Sorts L in place Common Tuple Methods T.method() Returns count(obj) Returns nbr of occurrences of obj in T index(obj) Returns index of first occurrence of obj in T; raises ValueError if obj is not in T Common Dictionary Methods D.method() Result/Returns clear() Remove all items from D get(k [,val]) Return D[k] if k in D, else val has_key(k) Return True if k in D, else False items() Return list of key-value pairs in D; each list item is 2-item tuple keys() Return list of D͛ƐŬĞLJƐ pop(k, [val]) Remove key k, return mapped value or val if k not in D values() Return list of D͛s values Common File Methods F.method() Result/Returns read([n]) Return str of next n chars from F, or up to EOF if n not given readline([n]) Return str up to next newline, or at most n chars if specified readlines() Return list of all lines in F, where each item is a line write(s) Write str s to F writelines(L) Write all str in seq L to F close() Closes the file Other Syntax Hold window for user keystroke to close: raw_input(͞Press to quit.͟) Prevent execution on import: ŝĨͺͺŶĂŵĞͺͺсс͞ͺͺŵĂŝŶͺͺ͗͟ main() Displayable ASCII Characters 32 SP 48 0 64 @ 80 P 96 ` 112 p 33 ! 49 1 65 A 81 Q 97 a 113 q 34 ͞ 50 2 66 B 82 R 98 b 114 r 35 # 51 3 67 C 83 S 99 c 115 s 36 $ 52 4 68 D 84 T 100 d 116 t 37 % 53 5 69 E 85 U 101 e 117 u 38 & 54 6 70 F 86 V 102 f 118 v 39 ͚ 55 7 71 G 87 W 103 g 119 w 40 ( 56 8 72 H 88 X 104 h 120 x 41 ) 57 9 73 I 89 Y 105 i 121 y 42 * 58 : 74 J 90 Z 105 j 122 z 43 + 59 ; 75 K 91 [ 107 k 123 { 44 , 60 < 76 L 92 \ 108 l 124 | 45 - 61 = 77 M 93 ] 109 m 125 } 46 . 62 > 78 N 94 ^ 110 n 126 ~ 47 / 63 ? 79 O 95 _ 111 o 127 DEL µ\¶ µ\W¶ µ\n¶ = 10

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