Changes between Version 1 and Version 4 of Ticket #26083


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Timestamp:
Jul 6, 2016, 12:13:15 AM (8 years ago)
Author:
Ben Finney
Comment:

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  • Ticket #26083

    • Property Triage Stage Unreviewed → Accepted
    • Property Summary __eq__, __hash__ and Python 3 → Python 2 deprecation warnings for classes that define __eq__() but not __hash__()

  • Ticket #26083 – Description

    v1 v4  
    1 I ran `python -Werror runtests.py` for DRF,  and noticed quite a lot of warnings about `__eq__` and `__hash__`, and then checked Django's repository.
     1Many classes within Django define the `__eq__` method, which in Python 3 will have disruptive implications for inheritance of `__hash__`. See the [https://docs.python.org/3.4/reference/datamodel.html#object.__hash__ Python 3 documentation for `__hash__`]:
    22
    3 `DeprecationWarning: Overriding __eq__ blocks inheritance of __hash__ in 3.x`
     3    If a class does not define an __eq__() method it should not define a __hash__() operation either; if it defines __eq__() but not __hash__(), its instances will not be usable as items in hashable collections. […]
     4
     5and continues on to describe in detail the implications of defining `__eq__` and/or `__hash__`, and exactly why one would implement one and/or the other on a class.
     6
     7The warning emitted by `python2 -3` for this is:
     8
     9    DeprecationWarning: Overriding __eq__ blocks inheritance of __hash__ in 3.x
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