Bruce Eckel wrote:
> Notice that both classes are identical, except that one inherits from
> dict (and works) and the other inherits from OrderedDict and fails.
> Has anyone seen this before? Thanks.
>
> import collections
>
> class Y(dict):
> def __init__(self, stuff):
> for k, v in stuff:
> self[k] = v
>
> # This works:
> print Y([('a', 'b'), ('c', 'd')])
>
> class X(collections.OrderedDict):
> def __init__(self, stuff):
> for k, v in stuff:
> self[k] = v
>
> # This doesn't:
> print X([('a', 'b'), ('c', 'd')])
>
> """ Output:
> {'a': 'b', 'c': 'd'}
> Traceback (most recent call last):
> File "OrderedDictInheritance.py", line 17, in <module>
> print X([('a', 'b'), ('c', 'd')])
> File "OrderedDictInheritance.py", line 14, in __init__
> self[k] = v
> File "C:\Python27\lib\collections.py", line 58, in __setitem__
> root = self.__root
> AttributeError: 'X' object has no attribute '_OrderedDict__root'
> """
Looks like invoking OrderedDict.__init__() is necessary:
>>> from collections import OrderedDict
>>> class X(OrderedDict):
... def __init__(self, stuff):
... super(X, self).__init__()
... for k, v in stuff:
... self[k] = v
...
>>> X([("a", "b"), ("c", "d")])
X([('a', 'b'), ('c', 'd')])
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