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Merged revisions 67243,67245,67277-67278,67289 via svnmerge from

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  r67243 | benjamin.peterson | 2008-11-17 15:39:05 -0600 (Mon, 17 Nov 2008) | 1 line

  a few fixes on the download page
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  r67245 | benjamin.peterson | 2008-11-17 16:05:19 -0600 (Mon, 17 Nov 2008) | 1 line

  improve __hash__ docs
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  r67277 | skip.montanaro | 2008-11-18 21:35:41 -0600 (Tue, 18 Nov 2008) | 1 line

  patch from issue 1108
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  r67278 | georg.brandl | 2008-11-19 01:59:09 -0600 (Wed, 19 Nov 2008) | 2 lines

  Try to fix problems with verbatim.
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  r67289 | brett.cannon | 2008-11-19 14:29:39 -0600 (Wed, 19 Nov 2008) | 2 lines

  Ignore .pyc and .pyo files.
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This commit is contained in:
Benjamin Peterson 2008-11-19 22:38:29 +00:00
parent 0f3641ce88
commit 6cadba718f
4 changed files with 19 additions and 15 deletions
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24
Doc/reference/datamodel.rst
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@ -1202,20 +1202,22 @@ Basic customization
object: dictionary
builtin: hash
Called for the key object for dictionary operations, and by the built-in
function :func:`hash`. Should return an integer usable as a hash value
for dictionary operations. The only required property is that objects which
compare equal have the same hash value; it is advised to somehow mix together
(e.g., using exclusive or) the hash values for the components of the object that
also play a part in comparison of objects.
Called by built-in function :func:`hash` and for operations on members of
hashed collections including :class:`set`, :class:`frozenset`, and
:class:`dict`. :meth:`__hash__` should return an integer. The only required
property is that objects which compare equal have the same hash value; it is
advised to somehow mix together (e.g. using exclusive or) the hash values for
the components of the object that also play a part in comparison of objects.
If a class does not define an :meth:`__eq__` method it should not define a
:meth:`__hash__` operation either; if it defines :meth:`__eq__` but not
:meth:`__hash__`, its instances will not be usable as dictionary keys. If a
class defines mutable objects and implements an :meth:`__eq__` method, it
should not implement :meth:`__hash__`, since the dictionary implementation
requires that a key's hash value is immutable (if the object's hash value
changes, it will be in the wrong hash bucket).
:meth:`__hash__`, its instances will not be usable as items in hashable
collections. If a class defines mutable objects and implements an
:meth:`__eq__` method, it should not implement :meth:`__hash__`, since the
implementation of hashable collections requires that a key's hash value is
immutable (if the object's hash value changes, it will be in the wrong hash
bucket).
User-defined classes have :meth:`__eq__` and :meth:`__hash__` methods
by default; with them, all objects compare unequal (except with themselves)