New submission from Krzysiek :
The documentation for `ArgumentParser.add_mutually_exclusive_group` states:
"argparse will make sure that only one of the arguments in the mutually
exclusive group was present on the command line".
This is not the case in certain circumstances:
Krzysiek added the comment:
It seems the discussion has so far revolved around 'optional' arguments with
`required=True`.
What about the other way around?
While trying to set `required=False` for a positional argument raises an
exception, it is still possible to make the
