Merged revisions 80030,80067,80069,80080-80081,80084,80432-80433,80465-80470,81059,81065-81067 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

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  r80030 | georg.brandl | 2010-04-13 08:43:54 +0200 (Di, 13 Apr 2010) | 1 line

  Get rid of multi-row cells.
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  r80067 | georg.brandl | 2010-04-14 10:53:38 +0200 (Mi, 14 Apr 2010) | 1 line

  #5341: typo.
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  r80069 | georg.brandl | 2010-04-14 15:50:31 +0200 (Mi, 14 Apr 2010) | 1 line

  Add an x-ref to where the O_ constants are documented and move the SEEK_ constants after lseek().
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  r80080 | georg.brandl | 2010-04-14 21:16:38 +0200 (Mi, 14 Apr 2010) | 1 line

  #8399: add note about Windows and O_BINARY.
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  r80081 | georg.brandl | 2010-04-14 23:34:44 +0200 (Mi, 14 Apr 2010) | 1 line

  #5250: document __instancecheck__ and __subclasscheck__.  I hope the part about the class/metaclass distinction is understandable.
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  r80084 | georg.brandl | 2010-04-14 23:46:45 +0200 (Mi, 14 Apr 2010) | 1 line

  Fix missing.
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  r80432 | georg.brandl | 2010-04-24 10:56:58 +0200 (Sa, 24 Apr 2010) | 1 line

  Markup fixes.
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  r80433 | georg.brandl | 2010-04-24 11:08:10 +0200 (Sa, 24 Apr 2010) | 1 line

  #7507: quote "!" in pipes.quote(); it is a special character for some shells.
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  r80465 | georg.brandl | 2010-04-25 12:29:17 +0200 (So, 25 Apr 2010) | 1 line

  Remove LaTeXy index entry syntax.
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  r80466 | georg.brandl | 2010-04-25 12:54:42 +0200 (So, 25 Apr 2010) | 1 line

  Patch from Tim Hatch: Better cross-referencing in socket and winreg docs.
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  r80467 | georg.brandl | 2010-04-25 12:55:16 +0200 (So, 25 Apr 2010) | 1 line

  Patch from Tim Hatch: Remove reference to winreg being the fabled high-level registry interface.
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  r80468 | georg.brandl | 2010-04-25 12:55:58 +0200 (So, 25 Apr 2010) | 1 line

  Patch from Tim Hatch: Minor spelling changes to _winreg docs.
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  r80469 | georg.brandl | 2010-04-25 12:56:41 +0200 (So, 25 Apr 2010) | 1 line

  Fix code example to have valid syntax so that it can be highlighted.
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  r80470 | georg.brandl | 2010-04-25 12:57:15 +0200 (So, 25 Apr 2010) | 1 line

  Patch from Tim Hatch: Make socket setblocking <-> settimeout examples symmetric.
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  r81059 | georg.brandl | 2010-05-10 23:02:51 +0200 (Mo, 10 Mai 2010) | 1 line

  #8642: fix wrong function name.
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  r81065 | georg.brandl | 2010-05-10 23:46:50 +0200 (Mo, 10 Mai 2010) | 1 line

  Fix reference direction.
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  r81066 | georg.brandl | 2010-05-10 23:50:57 +0200 (Mo, 10 Mai 2010) | 1 line

  Consolidate deprecation messages.
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  r81067 | georg.brandl | 2010-05-10 23:51:33 +0200 (Mo, 10 Mai 2010) | 1 line

  Fix typo.
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1 files changed, 40 insertions, 0 deletions

diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index 5af615d..06aa0f9 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -1587,6 +1587,46 @@ the new type and it saves the ordered dictionary keys in an attribute
 called *members*.
 
 
+Customizing instance and subclass checks
+----------------------------------------
+
+The following methods are used to override the default behavior of the
+:func:`isinstance` and :func:`issubclass` built-in functions.
+
+In particular, the metaclass :class:`abc.ABCMeta` implements these methods in
+order to allow the addition of Abstract Base Classes (ABCs) as "virtual base
+classes" to any class or type (including built-in types), and including to other
+ABCs.
+
+.. method:: class.__instancecheck__(self, instance)
+
+   Return true if *instance* should be considered a (direct or indirect)
+   instance of *class*. If defined, called to implement ``isinstance(instance,
+   class)``.
+
+
+.. method:: class.__subclasscheck__(self, subclass)
+
+   Return true if *subclass* should be considered a (direct or indirect)
+   subclass of *class*.  If defined, called to implement ``issubclass(subclass,
+   class)``.
+
+
+Note that these methods are looked up on the type (metaclass) of a class.  They
+cannot be defined as class methods in the actual class.  This is consistent with
+the lookup of special methods that are called on instances, only that in this
+case the instance is itself a class.
+
+.. seealso::
+
+   :pep:`3119` - Introducing Abstract Base Classes
+      Includes the specification for customizing :func:`isinstance` and
+      :func:`issubclass` behavior through :meth:`__instancecheck__` and
+      :meth:`__subclasscheck__`, with motivation for this functionality in the
+      context of adding Abstract Base Classes (see the :mod:`abc` module) to the
+      language.
+
+
 .. _callable-types:
 
 Emulating callable objects