[New-bugs-announce] [issue35341] Add generic version of OrderedDict to typing module
report at bugs.python.org
Wed Nov 28 12:17:38 EST 2018
New submission from Ismo Toijala <ismo.toijala at gmail.com>:
The other collections from the collections module (namedtuple, deque, ChainMap, Counter, defaultdict) have generic versions in the typing module for use in type annotations.
The problem is currently the following:
from __future__ import annotations
from collections import OrderedDict
# Understood by mypy
def f(d: OrderedDict[str, str]) -> None:
Traceback (most recent call last):
File "foo.py", line 9, in <module>
File "/usr/lib/python3.7/typing.py", line 1001, in get_type_hints
value = _eval_type(value, globalns, localns)
File "/usr/lib/python3.7/typing.py", line 260, in _eval_type
return t._evaluate(globalns, localns)
File "/usr/lib/python3.7/typing.py", line 464, in _evaluate
eval(self.__forward_code__, globalns, localns),
File "<string>", line 1, in <module>
TypeError: 'type' object is not subscriptable
To fix this, a line like the following could be added to Lib/typing.py near line 1250:
OrderedDict = _alias(collections.OrderedDict, (KT, VT))
There might be a reasoning for why this has not been done yet, but I have not been able to find any.
If this is acceptable, I could prepare a PR.
I suppose there is no hope of a backport to 3.7, since this is a new feature (though very minor).
components: Library (Lib)
title: Add generic version of OrderedDict to typing module
versions: Python 3.7, Python 3.8
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