New submission from Matěj Týč: I have an issue with passing default values to arguments. Basically, I would like to have a 'choices' argument (indicating something using capital letters) and perform custom action (adding boolean values to the args namespace). See the bottom of this post for rationale.
According to the documentation ( http://docs.python.org/2.7/library/argparse.html#default ), ... If the default value is a string, the parser parses the value as if it were a command-line argument. ... If this was true, I could implement a custom action. However, even if the default value is a string (as the documentation suggests), the action is bypassed. My goal is simple - I want to allow short choice-type argument (such as something.py --algorithm Q, the help would say --algorithhm Q|S, Q is quick, S is slow). Since the implementation shouldn't know about the mean one is communicating with the user, I would like to have the 'args' namespace either like (type='Q', quick=True, slow=False) or (type='quick') without giving up usage of the 'choices' pattern. If I change my mind and add a 'type' function that would expand capital letters abbreviations to full names, I will be OK with default values. However, if I pass the argument on the command-line, the type() call is performed first and the query whether the result is in the choices list fails. I consider the current behavior as a bug, IMO the action shouldn't be bypassed if the "default" is string. ---------- components: Library (Lib) messages: 193135 nosy: matej.tyc priority: normal severity: normal status: open title: argparse - problematic 'default' behavior type: behavior versions: Python 2.7 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue18467> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
