[New-bugs-announce] [issue35634] kwargs regression when there are multiple entries with the same key

[iceboy]

New submission from iceboy <spam at iceboy.org>:

Using the multidict package on pypi to illustrate the problem.

Python 3.5.3 (default, Sep 27 2018, 17:25:39) 
[GCC 6.3.0 20170516] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import multidict
>>> d = multidict.CIMultiDict([('a', 1), ('a', 2)])
>>> def foo(**kwargs): pass
... 
>>> foo(**d)
>>> foo(**{}, **d)

Python 3.6.7 (default, Oct 21 2018, 08:08:16) 
[GCC 8.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import multidict
>>> d = multidict.CIMultiDict([('a', 1), ('a', 2)])
>>> def foo(**kwargs): pass
... 
>>> foo(**d)
>>> foo(**{}, **d)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: foo() got multiple values for keyword argument 'a'

(1) foo(**d)
(2) foo(**{}, **d)

(1) works fine in both versions but (2) only works in Python 3.5 but raises TypeError in Python 3.6. This should be a regression. We should either make both expressions work or raises error.

----------
messages: 332849
nosy: iceboy
priority: normal
severity: normal
status: open
title: kwargs regression when there are multiple entries with the same key
versions: Python 3.6

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35634>
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