In Python, can I call the main() of an imported module?

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It’s just a function. Import it and call it:

import myModule

myModule.main()

If you need to parse arguments, you have two options:

  • Parse them in main(), but pass in sys.argv as a parameter (all code below in the same module myModule):

    def main(args):
    # parse arguments using optparse or argparse or what have you

if __name__ == '__main__':
    import sys
    main(sys.argv[1:])

    Now you can import and call myModule.main(['arg1', 'arg2', 'arg3']) from other another module.

  • Have main() accept parameters that are already parsed (again all code in the myModule module):

    def main(foo, bar, baz='spam'):
    # run with already parsed arguments

if __name__ == '__main__':
    import sys
    # parse sys.argv[1:] using optparse or argparse or what have you
    main(foovalue, barvalue, **dictofoptions)

    and import and call myModule.main(foovalue, barvalue, baz='ham') elsewhere and passing in python arguments as needed.

The trick here is to detect when your module is being used as a script; when you run a python file as the main script (python filename.py) no import statement is being used, so python calls that module "__main__". But if that same filename.py code is treated as a module (import filename), then python uses that as the module name instead. In both cases the variable __name__ is set, and testing against that tells you how your code was run.

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