paul j3 added the comment: The suggestion in this issue is to add a 'mutually_inclusive_group' mechanism, one that would let users specify that certain sets of arguments must occur together. Furthermore there was mention of allowing some sort of nesting.
Modeling it on the mutually_exclusive_group would be straight forward. But should it affect the usage and help display?mutually_exclusive_groups add a messy layer to the usage formatting. The only place such a group would act would be at the end of '_parse_known_args', where the current code checks for things like required actions (and mxgroups). A test at this point could use 'namespace', 'seen_actions' and 'seen_non_default_actions' to check whether the required group actions were seen. But the only thing that the argument_group contributes to this test is a list of argument names ('dest'?). Why not provide this list directly? And what if the user wants A to occur together with either B or C, but not both? Or make the inclusivity conditional on the value of A? Currently users can define argument interactions in a couple of ways. They can define custom Actions. In test_argparse.py there's a custom Actions test that does something like this (using '--spam' and 'badger'). But tests in Actions depend on the order in which arguments are given. An alternative is to test for interactions of arguments after `parse_args`. However the only information that the user has at this point is the args namespace. Reliably distinguishing between non-occurrence of arguments and default values can be difficult. I am proposing 'cross_test' mechanism that would give the user access to the 'seen_actions' and 'seen_non_default_actions' sets that 'mutually_exclusive_groups' use. Specifically an optional function can be called at the end of '_parse_known_args' that has access to these sets as well as the parser and the namespace. The core of the change would be adding cross_test = getattr(self, 'cross_test', None) if cross_test: cross_test(self, namespace, extras, seen_actions, seen_non_default_actions) at the end of 'parser._parse_known_args'. In addition 'cross_test' (or some other name) could be added to the 'ArgumentParser.__init__' arguments. The feature could be used by defining such a 'cross_test' function and adding it to the parser (either instance or subclass) def foobar(self, namespace, extras, seen_actions, seen_non_default_actions): ... (raise self.error(...)) parser.cross_test = foobar The patch proposed http://bugs.python.org/issue18943 should be included with any changes here since it refines the setting of 'seen_non_default_actions'. I am working on tests and examples of such functionality. ---------- nosy: +paul.j3 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue11588> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com