Inconsistency between dict() and collections.OrderedDict() methods.
ned at nedbatchelder.com
Sat Apr 29 18:40:29 EDT 2017
On Saturday, April 29, 2017 at 4:20:06 PM UTC-4, Erik wrote:
> It seems a little onerous that I have to put the key checks in several
> places and implement each of those APIs manually again (and keep on top
> of that if dict() grows some new methods that involve setting items). Is
> there a compelling reason why the dict module doesn't call a custom
> __setitem__ each time an item needs to be set? Performance is
> undoubtably a concern with something a fundamental as dicts...
Performance is the reason. For creating your own class that acts like
a dict, you should derive from collections.abc.MutableMapping, which
only requires implementing __getitem__, __setitem__, __delitem__,
__iter__, and __len__.
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