[docs] [issue16128] hashable documentation error

Max report at bugs.python.org
Thu Oct 4 13:37:14 CEST 2012

New submission from Max:

http://docs.python.org/dev/glossary.html?highlight=hashable says:

Objects which are instances of user-defined classes are hashable by default; they all compare unequal, and their hash value is their id().

Since x == x returns True by default, so "they all compare unequal" isn't quite right.

In addition, both the above paragraph and http://docs.python.org/dev/reference/datamodel.html?highlight=__eq__#object.__hash__ say:

User-defined classes have __eq__() and __hash__() methods by default; with them, all objects compare unequal (except with themselves) and x.__hash__() returns an appropriate value such that x == y implies both that x is y and hash(x) == hash(y).

This is correct, but may leave some confusion with the reader about what happens to a subclass of a built-in class (which doesn't use the default behavior, but instead simply inherits the parent's __hash__ and __eq__).

assignee: docs at python
components: Documentation
messages: 171935
nosy: docs at python, max
priority: normal
severity: normal
status: open
title: hashable documentation error
type: enhancement
versions: Python 3.2

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