[issue9625] argparse: Problem with defaults for variable nargs when using choices
João Eiras
report at bugs.python.org
Fri Jul 12 08:55:53 EDT 2019
João Eiras <joao.eiras at gmail.com> added the comment:
Another workaround for who might ever need it. The benefit of this solution comparing to a custom type is that argparse will generate the help string properly with the choices, and this solution does workaround the place when the bug happens:
class Choices(tuple):
# Python bug https://bugs.python.org/issue27227
def __new__(cls, *args, **kwargs):
x = tuple.__new__(cls, *args, **kwargs)
Choices.__init__(x, *args, **kwargs)
return x
def __init__(self, *args, **kwargs):
self.default = []
def __contains__(self, item):
return tuple.__contains__(self, item) or item is self.default
choices = Choices(("value1", "value2", "value3", ...))
parser.add_argument(
...,
nargs="*",
choices=choices,
default=choices.default,
...)
----------
nosy: +João Eiras
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