- 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
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
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).
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)
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)
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
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
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.
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)
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,
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)
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.
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 :
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
.
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.
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.
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