Python Modules Juancho Datu What is a Module

Python: Modules Juancho Datu

What is a Module? �File containing Python definitions and statements with the suffix ‘. py’ in the current directory �For example file name: � markov. py � Name becomes the global variable __name__ �Import into Python interpreter with: �import markov �Access functions in the module with: �markov. mca(alice 30. txt)

More about Modules �Global variables in module don’t affect the user’s global variables �Module variables can be accessed �modulename. itemname �Modules can import other modules �from markov import * � Placed at the beginning of importing module � * imports all names

Executing as Scripts �Can run a Python module with: �python markov. py <arguments> �Sets ‘__name__’ to ‘__main__’ � if __name__ == "__main__": � import sys � markov(str(sys. argv[1])) �Can be run as a script if above is placed at end of module �$ python markov. py alice 30. txt

Module Search Path �Can be modified in Unix �/usr/local/lib/python �Can be listed in: �Environment variable ‘PYTHONPATH’

‘Compiled’ Python Files �. pyc file created when. py is complied �‘byte-compiled’ version of the. py module �Can optimize code with –O or –OO flag �Creates. pyo files �Program doesn’t run faster with. pyc or. pyo �The modules are just loaded faster

Standard Modules �Comes with library of standard modules �‘sys’ module �sys. path can be used to modify PYTHONPATH � >>> import sys � >>> sys. path. append(‘[Path to be added]')

dir() Function �Returns sorted list of all the names defined by the module � >>> import sys � >>> dir(sys) � ['__displayhook__', '__doc__', '__excepthook__', '__name__', '__stderr__', '__stdin__', '__stdout__', '_getframe', 'api_version', 'argv', 'builtin_module_names', 'byteorder', 'callstats', 'copyright', 'displayhook', 'exc_clear', 'exc_info', 'exc_type', 'excepthook', 'exec_prefix', 'executable', 'exit', 'getdefaultencoding', 'getdlopenflags', 'getrecursionlimit', 'getrefcount', 'hexversion', 'maxint', 'maxunicode', 'meta_path', 'modules', 'path', 'path_hooks', 'path_importer_cache', 'platform', 'prefix', 'ps 1', 'ps 2', 'setcheckinterval', 'setdlopenflags', 'setprofile', 'setrecursionlimit', 'settrace', 'stderr', 'stdin', 'stdout', 'version', 'version_info', 'warnoptions']

Packages �Collection of modules �__init__. py starts the list of modules in a package

Packages cont. �Import individual modules �import sound. effects. echo �If ‘__init__. py’ includes � __all__ = ["echo", "surround", "reverse"] �Then the following statement would import those listed above � from sound. effects import * �‘__path__’ attribute is initialized with the list containing name of the directory holding package’s ‘__init__. py’ �Can be modified to extend set of modules in a package

Intra-package References �Sometimes modules in different subpackages need to reference a module in another subpackage �If ‘sound. filters. vocoder’ module needed to use ‘echo’ in the ‘sound. effects’ package: �from sound. effects import echo �Can also use implicit relative imports �from. import echo �from. . filters import equalizer

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