[docs] [issue14191] argparse doesn't allow optionals within positionals
report at bugs.python.org
Sat May 11 00:39:01 CEST 2013
paul j3 added the comment:
I should note one caveat:
As a consequence of setting nargs to 0 for the first 'parse_know_args' step, all positional entries in the namespace get an empty list value (). This is produced by 'ArgumentParser._get_values'. With the builtin action classes this does not cause any problems.
However a custom action class might have problems with this  value.
For example in 'test_argparse.py', TestActionUserDefined the PositionalAction class does check the values and throws an error with this  value.
The positional arguments are removed from the namespace before it is passed on to the 2nd 'parse_known_args', so these  in the first don't affect the final namespace.
I don't think anything about this should be added to main documentation, since it could confuse most readers. I might add a note of warning to the code itself.
Python tracker <report at bugs.python.org>
More information about the docs