paul j3 added the comment: A 'store_true' action takes 0 arguments. In effect `nargs=0`.
With an `optional` (flagged) argument, the default `False` is used if the flag is absent, and set to `True` when the flag is encountered (its Action `__call__` function is run). A `positional` is 'encountered' whenever there are enough values to meet its `nargs`. With `nargs=0`, an empty list of strings, i.e. none, is enough. Thus such a `positional` is always found, and its `__call__` is run, setting the value to `True`. As a result, action types like 'store_true', 'store_false', 'store_const' only make sense with `optionals`. And I can't think of simple way of using a 'positional' to set an Namespace 'dest' to boolean values. It could be done with a custom Action, but not with the predefined ones. Or you could translate the values after parsing. ---------- nosy: +paul.j3 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue22500> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
