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Diffstat (limited to 'Misc')
| -rw-r--r-- | Misc/cheatsheet | 127 |
1 files changed, 67 insertions, 60 deletions
diff --git a/Misc/cheatsheet b/Misc/cheatsheet index a4d96e2..828b54e 100644 --- a/Misc/cheatsheet +++ b/Misc/cheatsheet @@ -1,7 +1,7 @@ - Python 2.0 Quick Reference - + Python 2.3 Quick Reference + 25 Jan 2003 upgraded by Raymond Hettinger for Python 2.3 16 May 2001 upgraded by Richard Gruet and Simon Brunning for Python 2.0 2000/07/18 upgraded by Richard Gruet, rgruet@intraware.com for Python 1.5.2 from V1.3 ref @@ -19,32 +19,14 @@ Python's nest: http://www.python.org Developement: http:// python.sourceforge.net/ ActivePython : http://www.ActiveState.com/ASPN/ Python/ newsgroup: comp.lang.python Help desk: help@python.org -Resources: http://starship.python.net/ and http://www.vex.net/parnassus/ +Resources: http://starship.python.net/ + http://www.vex.net/parnassus/ + http://aspn.activestate.com/ASPN/Cookbook/Python +FAQ: http://www.python.org/cgi-bin/faqw.py Full documentation: http://www.python.org/doc/ -An excellent Python reference book: Python Essential Reference by David Beazley -(New Riders) - - -Contents - - * Invocation Options - * Environment Variables - * Lexical Entities : keywords, identifiers, strings, numbers, sequences, - dictionaries, operators - * Basic Types And Their Operations - * Advanced Types - * Statements - * Built In Functions - * Built In Exceptions - * Standard methods & operators redefinition in user-created Classes - * Special informative state attributes for some types - * Important Modules : sys, os, posix, posixpath, shutil, time, string, re, - math, getopt - * List of modules In base distribution - * Workspace Exploration And Idiom Hints - * Python Mode for Emacs - * The Python Debugger - +Excellent reference books: + Python Essential Reference by David Beazley (New Riders) + Python Pocket Reference by Mark Lutz (O'Reilly) Invocation Options @@ -53,18 +35,21 @@ python [-diOStuUvxX?] [-c command | script | - ] [args] Invocation Options Option Effect +-c cmd program passed in as string (terminates option list) -d Outputs parser debugging information (also PYTHONDEBUG=x) +-E ignore environment variables (such as PYTHONPATH) +-h print this help message and exit -i Inspect interactively after running script (also PYTHONINSPECT=x) and force prompts, even if stdin appears not to be a terminal --O Optimize generated bytecode (set __debug__ = 0 =>s suppresses asserts) +-O optimize generated bytecode (a tad; also PYTHONOPTIMIZE=x) +-OO remove doc-strings in addition to the -O optimizations +-Q arg division options: -Qold (default), -Qwarn, -Qwarnall, -Qnew -S Don't perform 'import site' on initialization -t Issue warnings about inconsistent tab usage (-tt: issue errors) -u Unbuffered binary stdout and stderr (also PYTHONUNBUFFERED=x). --U Force Python to interpret all string literals as Unicode literals. -v Verbose (trace import statements) (also PYTHONVERBOSE=x) +-W arg : warning control (arg is action:message:category:module:lineno) -x Skip first line of source, allowing use of non-unix Forms of #!cmd -[DEL:-X [DEL:Disable class based built-in exceptions (for backward -:DEL] compatibility management of exceptions):DEL] -? Help! -c Specify the command to execute (see next section). This terminates the command option list (following options are passed as arguments to the command). @@ -115,7 +100,7 @@ Keywords assert elif from lambda return break else global not try class except if or while - continue exec import pass + continue exec import pass yield def finally in print * (list of keywords in std module: keyword) @@ -174,9 +159,9 @@ Strings Numbers Decimal integer: 1234, 1234567890546378940L (or l) - Octal integer: 0177, 0177777777777777777L (begin with a 0) - Hex integer: 0xFF, 0XFFFFffffFFFFFFFFFFL (begin with 0x or 0X) - Long integer (unlimited precision): 1234567890123456L (ends with L or l) + Octal integer: 0177, 0177777777777777777 (begin with a 0) + Hex integer: 0xFF, 0XFFFFffffFFFFFFFFFF (begin with 0x or 0X) + Long integer (unlimited precision): 1234567890123456 Float (double precision): 3.14e-10, .001, 10., 1E3 Complex: 1J, 2+3J, 4+5j (ends with J or j, + separates (float) real and imaginary parts) @@ -206,8 +191,12 @@ a = (0,1,2,3,4,5,6,7) Dictionaries (Mappings) - Dictionary of length 0, 1, 2, etc: - {} {1 : 'first'} {1 : 'first', 'next': 'second'} + {} # Zero length empty dictionary + {1 : 'first'} # Dictionary with one (key, value) pair + {1 : 'first', 'next': 'second'} + dict([('one',1),('two',2)]) # Construct a dict from an item list + dict('one'=1, 'two'=2) # Construct a dict using keyword args + dict.fromkeys(['one', 'keys']) # Construct a dict from a sequence Operators and their evaluation order @@ -235,7 +224,10 @@ Highest Operator Comment Lowest lambda args: expr anonymous function Alternate names are defined in module operator (e.g. __add__ and add for +) -Most operators are overridable +Most operators are overridable. + +Many of binary operators support augmented assignment: + x += 1 # Same as x = x + 1 Basic Types and Their Operations @@ -256,6 +248,9 @@ is not negated object identity (2) Notes : Comparison behavior can be overridden for a given class by defining special method __cmp__. + The above comparisions return True or False which are of type bool +(a subclass of int) and behave exactly as 1 or 0 except their type and +that they print as True or False instead of 1 or 0. (1) X < Y < Z < W has expected meaning, unlike C (2) Compare object identities (i.e. id(object)), not object values. @@ -344,6 +339,7 @@ Operations on all sequence types (lists, tuples, strings) Operation Result Notes x in s 1 if an item of s is equal to x, else 0 x not in s 0 if an item of s is equal to x, else 1 +for x in s: loops over the sequence s + t the concatenation of s and t s * n, n*s n copies of s concatenated s[i] i'th item of s, origin 0 (1) @@ -351,6 +347,7 @@ s[i:j] slice of s from i (included) to j (excluded) (1), (2) len(s) length of s min(s) smallest item of s max(s) largest item of (s) +iter(s) returns an iterator over s. iterators define __iter__ and next() Notes : (1) if i or j is negative, the index is relative to the end of the string, @@ -370,12 +367,12 @@ s[i] =x item i of s is replaced by x s[i:j] = t slice of s from i to j is replaced by t del s[i:j] same as s[i:j] = [] s.append(x) same as s[len(s) : len(s)] = [x] -s.extend(x) same as s[len(s):len(s)]= x (5) s.count(x) return number of i's for which s[i] == x +s.extend(x) same as s[len(s):len(s)]= x s.index(x) return smallest i such that s[i] == x (1) s.insert(i, x) same as s[i:i] = [x] if i >= 0 -s.remove(x) same as del s[s.index(x)] (1) s.pop([i]) same as x = s[i]; del s[i]; return x (4) +s.remove(x) same as del s[s.index(x)] (1) s.reverse() reverse the items of s in place (3) s.sort([cmpFct]) sort the items of s in place (2), (3) @@ -391,12 +388,8 @@ considered smaller than, equal to, or larger than the 2nd of space when sorting or reversing a large list. They don't return the sorted or reversed list to remind you of this side effect. - (4) [New 1.5.2] The pop() method is experimental and not supported by -other mutable sequence types than lists. - The optional argument i defaults to -1, so that by default the last + (4) [New 1.5.2] The optional argument i defaults to -1, so that by default the last item is removed and returned. - (5) [New 1.5.2] Experimental ! Raises an exception when x is not a list -object. @@ -410,12 +403,18 @@ d[k] = x set d[k] to x del d[k] remove d[k] from d (1) d.clear() remove all items from d d.copy() a shallow copy of d +d.get(k,defaultval) the item of d with key k (4) d.has_key(k) 1 if d has key k, else 0 d.items() a copy of d's list of (key, item) pairs (2) +d.iteritems() an iterator over (key, value) pairs (7) +d.iterkeys() an iterator over the keys of d (7) +d.itervalues() an iterator over the values of d (7) d.keys() a copy of d's list of keys (2) d1.update(d2) for k, v in d2.items(): d1[k] = v (3) d.values() a copy of d's list of values (2) -d.get(k,defaultval) the item of d with key k (4) +d.pop(k) remove d[k] and return its value +d.popitem() remove and return an arbitrary (6) + (key, item) pair d.setdefault(k,defaultval) the item of d with key k (5) Notes : @@ -431,6 +430,9 @@ d.setdefault(k,defaultval) the item of d with key k (5) defaultVal, and adds k to map with value defaultVal. defaultVal is optional. When not provided and k is not in the map, None is returned and added to map. + (6) Raises a KeyError if the dictionary is emtpy. + (7) While iterating over a dictionary, the values may be updated but + the keys cannot be changed. Operations on strings @@ -446,30 +448,33 @@ s.center(width) return a copy of s centered in a string of length width (1) . s.count(sub[ return the number of occurrences of substring sub in (2) ,start[,end]]) string s. +s.decode(([ return a decoded version of s. (3) + encoding + [,errors]]) s.encode([ return an encoded version of s. Default encoding is the -encoding[,errors current default string encoding. (3) -]]) + encoding current default string encoding. (3) + [,errors]]) s.endswith(suffix return true if s ends with the specified suffix, (2) -[,start[,end]]) otherwise return false. + [,start[,end]]) otherwise return False. s.expandtabs([ return a copy of s where all tab characters are (4) tabsize]) expanded using spaces. s.find(sub[,start return the lowest index in s where substring sub is (2) [,end]]) found. Return -1 if sub is not found. s.index(sub[ like find(), but raise ValueError when the substring is (2) ,start[,end]]) not found. -s.isalnum() return true if all characters in s are alphanumeric, (5) - false otherwise. -s.isalpha() return true if all characters in s are alphabetic, (5) - false otherwise. -s.isdigit() return true if all characters in s are digit (5) - characters, false otherwise. -s.islower() return true if all characters in s are lowercase, false (6) +s.isalnum() return True if all characters in s are alphanumeric, (5) + False otherwise. +s.isalpha() return True if all characters in s are alphabetic, (5) + False otherwise. +s.isdigit() return True if all characters in s are digit (5) + characters, False otherwise. +s.islower() return True if all characters in s are lowercase, False (6) otherwise. -s.isspace() return true if all characters in s are whitespace (5) - characters, false otherwise. -s.istitle() return true if string s is a titlecased string, false (7) +s.isspace() return True if all characters in s are whitespace (5) + characters, False otherwise. +s.istitle() return True if string s is a titlecased string, False (7) otherwise. -s.isupper() return true if all characters in s are uppercase, false (6) +s.isupper() return True if all characters in s are uppercase, False (6) otherwise. s.join(seq) return a concatenation of the strings in the sequence seq, seperated by 's's. @@ -503,6 +508,8 @@ s.title() uppercase characters, all remaining cased characters s.translate(table return a copy of s mapped through translation table (12) [,deletechars]) table. s.upper() return a copy of s converted to uppercase. +s.zfill(width) return a string padded with zeroes on the left and + sliding a minus sign left if necessary. never truncates. Notes : (1) Padding is done using spaces. |