Launch Python debugger while simultaneously executing module as script

Question

When developing a Python package, it\'s very convenient to use the -m option to run modules inside the package as scripts for quick testing. For example, for

Answer 1

Here's another option that also works with command line arguments.

It's generally a good idea to wrap your script's logic in a main function. You can then have main take in an optional list of arguments to override sys.argv. Here's an example called argdemo.py:

def main(cmd_line_args=None):
    import argparse

    parser = argparse.ArgumentParser()
    parser.add_argument("number", help="a number", type=int)

    # allow cmd_line_args to override sys.argv
    if cmd_line_args is None:
        args = parser.parse_args()
    else:
        args = parser.parse_args(cmd_line_args)

    print("The number is {}".format(args.number))

if __name__ == '__main__':
    main()

This module can be run as usual:

$ python -m argdemo 2
> The number is 2

Or it can be run with pdb by calling main() directly:

$ python -c "import pdb; import argdemo; pdb.runcall(argdemo.main, ['2'])"
(Pdb) continue
> The number is 2

(Notice that cmd_line_args has to be a list of strings just like argv would be).

As an added bonus, when your module has an import-able main function, you can write unit tests for it in the same way =)