notes:python_cheat_sheet
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notes:python_cheat_sheet [2026/06/05 03:51] 150.5.131.139 old revision restored (2026/05/23 19:49) |
notes:python_cheat_sheet [2026/06/07 13:59] (current) 150.5.134.52 old revision restored (2026/06/03 02:44) |
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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 | + | * Lists can be created from sequences |
| vec = [2, 4, 6] | vec = [2, 4, 6] | ||
| - | [[x, x**2] for x in vec] | + | [[x, x**2] for x in vec if x > 2] |
| - | [[2, 4], [4, 16], [6, 36]]</ | + | [[4, 16], [6, 36]] |
| + | [x+y for x in vec for y in vec2 if x > 2]</ | ||
| * 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)). | ||
| Line 54: | Line 55: | ||
| * But strings can't be modified using slices or indexes. | * But strings can't be modified using slices or indexes. | ||
| * [[http:// | * [[http:// | ||
| - | * format-string % (tuple) allows use of printf formatting strings. Also string.format() . | ||
| ===== Control Flow ===== | ===== Control Flow ===== | ||
| Line 85: | Line 85: | ||
| * 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 ===== | + | ===== Modules |
| + | |||
| + | * A //module// is a file of python definitions. | ||
| + | * Definitions in a module can be accessed by importing the module. <code python> | ||
| + | from fib import fib1, fib2 | ||
| + | </ | ||
| + | * <code python> | ||
| + | * 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. | ||
| + | * 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/ | ||
| + | |||
| + | * str() returns a readable representations, | ||
| + | * Strings have several formatting methods. | ||
| + | * [[ http:// | ||
| + | * To open a file <code python> open('/ | ||
| + | * File methods include read, readline, write. | ||
| + | * //pickle// contains load and dump methods for serializing objects. Support should be added for new object types. | ||
notes/python_cheat_sheet.1780656683.txt.gz · Last modified: 2026/06/05 03:51 by 150.5.131.139
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