From: Batuhan Taşkaya <47358913+isidentical@users.noreply.github.com>
Date: Tue, 19 Nov 2019 08:16:46 +0000 (+0300)
Subject: bpo-21767: explicitly mention abc support in functools.singledispatch docs (#17171)
X-Git-Tag: v3.9.0a1~1
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=24555ce2f969bd69517011d23aaf8cc481090211;p=thirdparty%2FPython%2Fcpython.git

bpo-21767: explicitly mention abc support in functools.singledispatch docs (#17171)
---

diff --git a/Doc/library/functools.rst b/Doc/library/functools.rst
index cedc3ad5ec0a..bb7aac42daca 100644
--- a/Doc/library/functools.rst
+++ b/Doc/library/functools.rst
@@ -423,6 +423,20 @@ The :mod:`functools` module defines the following functions:
    for the base ``object`` type, which means it is used if no better
    implementation is found.
 
+   If an implementation registered to :term:`abstract base class`, virtual
+   subclasses will be dispatched to that implementation::
+
+     >>> from collections.abc import Mapping
+     >>> @fun.register
+     ... def _(arg: Mapping, verbose=False):
+     ...     if verbose:
+     ...         print("Keys & Values")
+     ...     for key, value in arg.items():
+     ...         print(key, "=>", value)
+     ...
+     >>> fun({"a": "b"})
+     a => b
+
    To check which implementation will the generic function choose for
    a given type, use the ``dispatch()`` attribute::
 
diff --git a/Misc/NEWS.d/next/Documentation/2019-11-17-11-54-57.bpo-21767.Qq3Dos.rst b/Misc/NEWS.d/next/Documentation/2019-11-17-11-54-57.bpo-21767.Qq3Dos.rst
new file mode 100644
index 000000000000..1e2a45e1113c
--- /dev/null
+++ b/Misc/NEWS.d/next/Documentation/2019-11-17-11-54-57.bpo-21767.Qq3Dos.rst
@@ -0,0 +1 @@
+Explicitly mention abc support in functools.singledispatch