[New-bugs-announce] [issue27588] Type objects are hashable and comparable for equality but this is not documented

[Gareth Rees]

New submission from Gareth Rees:

The type objects constructed by the metaclasses in the typing module are hashable and comparable for equality:

    >>> from typing import *
    >>> {Mapping[str, int], Mapping[int, str]}
    {typing.Mapping[int, str], typing.Mapping[str, int]}
    >>> Union[str, int, float] == Union[float, int, str]
    True
    >>> List[int] == List[float]
    False

but this is not clearly documented in the documentation for the typing module (there are a handful of examples using equality, but it's not explicit that these are runnable).

It would be nice if there were explicit documentation for these properties of type objects.

----------
assignee: docs at python
components: Documentation
messages: 270981
nosy: Gareth.Rees, docs at python
priority: normal
severity: normal
status: open
title: Type objects are hashable and comparable for equality but this is not documented
type: enhancement
versions: Python 3.5, Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue27588>
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