Raps Uk <rap...@gmail.com> added the comment:
Taking the union of items() in Python 3 (viewitems() in Python 2.7) will also
fail when values are unhashable objects (like lists, for example). Even if your
values are hashable, since sets are semantically unordered, the behavior is
undefined in regards to precedence. So don't do this:
>>> c = dict(a.items() | b.items())
This example demonstrates what happens when values are unhashable:
>>> x = {'a': []}
>>> y = {'b': []}
>>> dict(x.items() | y.items())
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
Here's an example where y should have precedence, but instead the value from x
is retained due to the arbitrary order of sets:
>>> x = {'a': 2}
>>> y = {'a': 1}
>>> dict(x.items() | y.items())
{'a': 2}
http://net-informations.com/python/ds/merge.htm
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nosy: +Raps Uk
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue36144>
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