New submission from Zahari Dim:
When trying to see if the keys() of a collections.ChainMap object are empty, it
tries to compute the hash of the dicts that compose the ChainMap, giving rise
to an error:
In [1]: from collections import ChainMap
In [2]: m = ChainMap([{'a':1}, {'b':2}])
In [3]: bool(m.keys())
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-3-365f7b817ebf> in <module>()
----> 1 bool(m.keys())
/home/zah/anaconda3/lib/python3.5/_collections_abc.py in __len__(self)
633
634 def __len__(self):
--> 635 return len(self._mapping)
636
637 def __repr__(self):
/home/zah/anaconda3/lib/python3.5/collections/__init__.py in __len__(self)
865
866 def __len__(self):
--> 867 return len(set().union(*self.maps)) # reuses stored hash
values if possible
868
869 def __iter__(self):
TypeError: unhashable type: 'dict'
Also, I can't ask if 'a' is in keys:
In [6]: m.keys()
Out[6]: KeysView(ChainMap([{'a': 1}, {'b': 2}]))
In [9]: ks = m.keys()
In [17]: 'a' in ks
Out[17]: False
----------
components: Library (Lib)
messages: 269370
nosy: Zahari.Dim
priority: normal
severity: normal
status: open
title: ChainMap.keys() is broken
versions: Python 3.5
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue27399>
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