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notes:python_cheat_sheet [2026/06/13 16:14]
114.119.151.209 old revision restored (2026/06/08 14:43) 		notes:python_cheat_sheet [2026/06/13 16:16] (current)
114.119.135.121 old revision restored (2026/06/08 13:36)
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 [[http://www.python.org/ | Python]] is a dynamic object-oriented programming language with extensive standard libraries. These notes summarize the [[http://docs.python.org/3.0/tutorial/ | Python 3.0 tutorial]]. [[http://www.python.org/ | Python]] is a dynamic object-oriented programming language with extensive standard libraries. These notes summarize the [[http://docs.python.org/3.0/tutorial/ | Python 3.0 tutorial]].
 +
 +===== The Interpreter =====
 +
   * **python**/**python3.0** is the command-line interpreter with readline where available.   * **python**/**python3.0** is the command-line interpreter with readline where available.
   * python -c command runs a single command.   * python -c command runs a single command.
-  * %%>>> prompts for a line . ... prompts for a continuation of a previous line.%%+  * sys.argv is a list of strings with the script if any in sys.argv[0] 
 +  * >>> prompts for a line . ... prompts for a continuation of a previous line
   * PYTHONSTARTUP can point to a file of startup commands   * PYTHONSTARTUP can point to a file of startup commands
   * Expressions are evaluated and printed.   * Expressions are evaluated and printed.
   * The last printed expression is assigned to _ .   * The last printed expression is assigned to _ .
 +
  
 ===== Basics ===== ===== Basics =====
   * Comments start with # .   * Comments start with # .
-  * sys.argv is a list of strings with the script if any in sys.argv[0] 
   * Variables can be assigned (using = ) without being defined but must be assigned before being used.   * Variables can be assigned (using = ) without being defined but must be assigned before being used.
   * a,b = c,d does a multiple assignment.   * a,b = c,d does a multiple assignment.
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   * Lists can be nested.   * Lists can be nested.
   * Other methods include append, pop, extend, index, count, sort, reverse.   * Other methods include append, pop, extend, index, count, sort, reverse.
-  * Lists can be created from sequences using list comprehension <code python>+  * Lists can be created from sequences e.g <code python>
 vec = [2, 4, 6] vec = [2, 4, 6]
-[[x, x**2] for x in vec if x > 2] +[[x, x**2] for x in vec] 
-[[4, 16], [6, 36]] +[[2, 4], [4, 16], [6, 36]]</code>
-[x+y for x in vec for y in vec2 if x > 2]</code>+
   * Other sequence types include tuples ( (1,2) or 1,2) and sets ({1,2} or set(1,2)).   * Other sequence types include tuples ( (1,2) or 1,2) and sets ({1,2} or set(1,2)).
  
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   * But strings can't be modified using slices or indexes.   * But strings can't be modified using slices or indexes.
   * [[http://docs.python.org/3.0/library/stdtypes.html#string-methods | String methods]] include strip, format, capitalize etc.   * [[http://docs.python.org/3.0/library/stdtypes.html#string-methods | String methods]] include strip, format, capitalize etc.
 +  * format-string % (tuple) allows use of printf formatting strings. Also string.format() .
  
 ===== Control Flow ===== ===== Control Flow =====
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   * zip takes two or more lists with the same number of elements and creates a single list of lists with corresponding members grouped together.   * zip takes two or more lists with the same number of elements and creates a single list of lists with corresponding members grouped together.
  
-===== Modules & Packages =====+===== Modules =====
  
   * A //module// is a file of python definitions.   * A //module// is a file of python definitions.
-  * Definitions in a module can be accessed by importing the module. <code python>import fib+  * Definitions in a module can be accessed by importing the module. <code python> import fib
 from fib import fib1, fib2 from fib import fib1, fib2
 </code> </code>
-  * %%__name__%% is set to the name of the module or to %%__main__%% if called from the command line.+  * __name__ is set to the name of the module or to __main__ if called from the command line.
   * The search list for modules is the variable sys.path initialized from the directory containing the input script (or the current directory), PYTHONPATH and the installation-dependent default.   * The search list for modules is the variable sys.path initialized from the directory containing the input script (or the current directory), PYTHONPATH and the installation-dependent default.
   * When a module is imported, a byte-code version is stored to module.pyc which speeds up successive loads.   * When a module is imported, a byte-code version is stored to module.pyc which speeds up successive loads.
-  * There are many standard modules including sys which is common to all platforms. + * There are many standard modules including sys which is common to all platforms.
-  * dir(module) lists all names in a module sorted alphabetically. dir(builtins) shows all the built-in functions and variables. +
-  * Packages can be used to group modules. Packages should be in a named directory with an __init__.py file optionally containing initialization code. E.g. import sound.effects.echo . +
-  * . is the current package, .. is the parent package etc. +
- +
-===== Input/Output ===== +
- +
-  * str() returns a readable representations, repr() returns a canonical representation +
-  * Strings have several formatting methods.  +
-  * //formatstring.format(tuple)// is the [[http://docs.python.org/3.0/library/string.html#formatspec | new-style printf]] equivalent. The [[http://docs.python.org/3.0/library/stdtypes.html#old-string-formatting | old-style]] was //formatstring % (tuple)// which uses C-type format strings. +
-  * To open a file <code python> open('/tmp/workfile', 'w') </code> +
-  * [[http://docs.python.org/3.0/library/stdtypes.html#file-objects | File methods]] include read, readline, write. +
-  * //pickle// contains [[http://docs.python.org/3.0/library/pickle.html | load and dump methods]] for serializing objects. Support should be added for new object types.+
notes/python_cheat_sheet.txt · Last modified: 2026/06/13 16:16 by 114.119.135.121

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