Will OrderedDict become redundant in Python 3.7?
Question:
From the Python 3.7 changelog:
the insertion-order preservation nature of dict objects has been declared to be an official part of the Python language spec.
Would this mean that OrderedDict will become redundant? The only use I can think of it will be to maintain backwards compatibility with older versions of Python which don’t preserve insertion-order for normal dictionaries.
Answers:
No it won’t become redundant in Python 3.7 because OrderedDict is not just a dict that retains insertion order, it also offers an order dependent method, OrderedDict.move_to_end(), and supports reversed() iteration*.
Moreover, equality comparisons with OrderedDict are order sensitive and this is still not the case for dict in Python 3.7, for example:
>>> OrderedDict([(1,1), (2,2)]) == OrderedDict([(2,2), (1,1)])
False
>>> dict([(1,1), (2,2)]) == dict([(2,2), (1,1)])
True
Two relevant questions here and here.
* Support for reversed() iteration of regular Python dict is added for Python 3.8, see issue33462
From the Python 3.7 changelog:
the insertion-order preservation nature of dict objects has been declared to be an official part of the Python language spec.
Would this mean that OrderedDict will become redundant? The only use I can think of it will be to maintain backwards compatibility with older versions of Python which don’t preserve insertion-order for normal dictionaries.
No it won’t become redundant in Python 3.7 because OrderedDict is not just a dict that retains insertion order, it also offers an order dependent method, OrderedDict.move_to_end(), and supports reversed() iteration*.
Moreover, equality comparisons with OrderedDict are order sensitive and this is still not the case for dict in Python 3.7, for example:
>>> OrderedDict([(1,1), (2,2)]) == OrderedDict([(2,2), (1,1)])
False
>>> dict([(1,1), (2,2)]) == dict([(2,2), (1,1)])
True
Two relevant questions here and here.
* Support for reversed() iteration of regular Python dict is added for Python 3.8, see issue33462