[docs] [issue16697] argparse kwarg 'choices' documentation

[wim glenn]

New submission from wim glenn:

Any object that supports the in operator can be passed as the choices value, so dict objects, set objects, custom containers, etc. are all supported.  (from  http://docs.python.org/dev/library/argparse.html#choices )

Actual behaviour is contradicted by the docs - it seems the container must additionally be iterable.  When using a custom container, argparse b0rks on trying to iterate through choices.  Using a metavar prevents this, but it still breaks on cases where the element is not in the container.  

More details here:  
http://stackoverflow.com/questions/13833566/python-argparse-choices-from-an-infinite-set

----------
assignee: docs at python
components: Documentation
messages: 177599
nosy: docs at python, wim.glenn
priority: normal
severity: normal
status: open
title: argparse kwarg 'choices' documentation
type: enhancement
versions: Python 2.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue16697>
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