New submission from Wolfgang Maier <wolfgang.ma...@biologie.uni-freiburg.de>:
I find the True default for 'required' quite cumbersome introduced as a result of issue 26510. With existing parsers it can unnecessarily break compatibility between Python3.x versions only to make porting a bit easier for Python2 users. I think, this late in the life cycle of Python2, within Python3 compatibility should be ranked higher than py2to3 portability. Command line parsing of a package of mine has long used optional subparsers (without me even thinking much about the fact). Now in 3.7, running python3.7 -m MyPackage without arguments (the parser is in __main__.py) I get the ill-formatted error message: __main__.py: error: the following arguments are required: while my code in 3.3 - 3.6 was catching the empty Namespace returned and printed a help message. Because the 'required' keyword argument did not exist in < 3.7 there was no simple way for me to write code that is compatible between all 3.x versions. What I ended up doing now is to check sys.argv before trying to parse things, then print the help message, when that only has a single item, just to keep my existing code working. OTOH, everything would be just fine with a default value of False. Also that truncated error message should be fixed before 3.7 gets released. ---------- components: Library (Lib) messages: 314145 nosy: Anthony Sottile, bethard, eric.araujo, memeplex, paul.j3, wolma priority: normal severity: normal status: open title: argparse: make new 'required' argument to add_subparsers default to False instead of True type: behavior versions: Python 3.7, Python 3.8 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue33109> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
