New submission from Joel Nothman:
The argparse documentation states that "type= can take any callable that takes
a single string argument and returns the converted value". The following is an
exception:
>>> import argparse
>>> ap = argparse.ArgumentParser()
>>> ap.add_argument('foo', type={}.get)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3/argparse.py", line 1294, in add_argument
type_func = self._registry_get('type', action.type, action.type)
File "/usr/lib/python3/argparse.py", line 1236, in _registry_get
return self._registries[registry_name].get(value, default)
TypeError: unhashable type: 'dict'
Sadly, a method bound to an unhashable type is unhashable! (Of course, is
trivial to use partial or lambda to make any function hashable.)
The offending line in _registry_get is intended to look up named types (or
actions), so it perhaps only relevant for string type= and action= values,
which could be handled explicitly instead of using dict.get(x, x) to handle
both cases. Alternatively, the TypeError could be caught and default returned.
----------
components: Library (Lib)
messages: 176040
nosy: bethard, jnothman
priority: normal
severity: normal
status: open
title: argparse types (and actions) must be hashable
type: behavior
versions: Python 2.7, Python 3.4
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue16516>
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