Sometimes it would be nice to be able to supply defaults as strings, and have the ArgumentParser parse them. For example, if you had a matrix type, that converted "zero" to, say, [[0, 0, 0], [0, 0, 0], [0, 0, 0]], then you might want your default value to still be "zero" for the purposes of help, so you'd like to write::

parser.add_argument(..., default="zero", ...)

Right now, defaults are not parsed, so this would fail. It would be nice if you could supply, say, parse_defaults=True to the ArgumentParser constructor to make this work.

I think this isn't actually an issue - type conversion is done for any string argument value, even if that value came from the default::

def simple_list(string): ... return string.split(",") ... parser = argparse.ArgumentParser() parser.add_argument('foo', nargs='?', type=simple_list, default="a,b,c") parser.parse_args([]) Namespace(foo=['a', 'b', 'c'])

So basically, this should already work.