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notes:python_cheat_sheet [2026/09/13 21:37] 102.66.147.176 old revision restored (2026/08/07 00:12) |
notes:python_cheat_sheet [2026/09/15 03:45] (current) 59.103.33.23 old revision restored (2026/08/06 22:23) |
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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 if x > 2] | + | [[x, x**2] for x in vec] |
| - | [[4, 16], [6, 36]] | + | [[2, 4], [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 86: | 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. | * A //module// is a file of python definitions. | ||
| - | * Definitions in a module can be accessed by importing the module. <code python> | + | * 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 | ||
| </ | </ | ||
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| * 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. |
| - | * 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. | + | |