[issue45338] Add key argument to collections.Counter
New submission from kubat aytekin : Counter has become the default tool for counting occurences of objects in an iterable. However by construction it only works on hashable objects as it is a subclass of dict. Would it be possible to implement a "key=" keyword argument as in sort etc.? Here's a stackoverflow question wherein either map or implementing a hash method was proposed: https://stackoverflow.com/questions/69401713/elegant-way-of-counting-items-in-a-list-by-enum-value-in-python -- components: Library (Lib) messages: 403002 nosy: kubataytekin priority: normal severity: normal status: open title: Add key argument to collections.Counter type: enhancement versions: Python 3.11 ___ Python tracker <https://bugs.python.org/issue45338> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue45338] Add key argument to collections.Counter
kubat aytekin added the comment: I was thinking about use cases where one might want to preserve the original key. I was not however aware of PEP 455 and the reasons for it's rejection. My bad. Yet It is still unclear to me what the best practice would be to reverse lookup unhashable objects. Say you have a list of objects from which you need the most common. If there is no good way of reversing the transform, your only option is iterating trough your list? Which defeats the purpose of using a Counter and you'd be better off counting explicitly. Maybe I'm imagining unrealistic/far-fetched use cases. -- ___ Python tracker <https://bugs.python.org/issue45338> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue45338] Add key argument to collections.Counter
kubat aytekin added the comment: Or keep the reverse mapping in another dict: count = Counter() reverse_mapping = dict() for x in all_the_items: count.update(keyfunc(x)) reverse_mapping[keyfunc(x)] = x Anyways I'm closing it as it is a partial duplicate of key-transforming dictionaries. -- resolution: -> duplicate stage: -> resolved status: open -> closed ___ Python tracker <https://bugs.python.org/issue45338> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
