New submission from Chris Jerdonek: This issue is to ensure that argparse.ArgumentParser() accepts objects that support the "in" operator for the "choices" argument to ArgumentParser.add_argument().
As observed by Terry in the comments to issue 16418: http://bugs.python.org/issue16418#msg175520 the argparse module does not in general support "choices" values that support the "in" operator, even though the argparse documentation says it does: "Any object that supports the in operator can be passed as the choices value, so dict objects, set objects, custom containers, etc. are all supported." (from http://docs.python.org/2/library/argparse.html#choices ) For example, passing a user-defined type that implements only self.__contains__() yields the following error message when calling ArgumentParser.parse_args(): File ".../Lib/argparse.py", line 1293, in add_argument raise ValueError("length of metavar tuple does not match nargs") (The error message also gives the wrong reason for failure. The swallowed exception is "TypeError: '<class>' object is not iterable.") ---------- components: Library (Lib) messages: 175534 nosy: chris.jerdonek, terry.reedy priority: normal severity: normal status: open title: argparse only supports iterable choices type: behavior versions: Python 2.7, Python 3.2, Python 3.3, Python 3.4 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue16468> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
