From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Sat, 13 Jul 2024 20:13:52 +0000 (+0200)
Subject: [3.12] gh-73159 Added clarifications in multiprocessing docs on that objects are... 
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X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b6cb209d5de4ac64ffe4e79432909967f91635cb;p=thirdparty%2FPython%2Fcpython.git

[3.12] gh-73159 Added clarifications in multiprocessing docs on that objects are pickled. (GH-121686) (#121728)

gh-73159 Added clarifications in multiprocessing docs on that objects are pickled. (GH-121686)

Added explicit comments about that objects are pickled when transmitted via multiprocessing queues and pipes.
(cherry picked from commit b5805892d55e769335c11a994b586355720263ba)

Co-authored-by: Ulrik Södergren <ulrik@digitalfotografen.se>
---

diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index d6474ef975b5..f12d4e31b4fe 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -254,6 +254,7 @@ processes:
           p.join()
 
    Queues are thread and process safe.
+   Any object put into a :mod:`~multiprocessing` queue will be serialized.
 
 **Pipes**
 
@@ -281,6 +282,8 @@ processes:
    of corruption from processes using different ends of the pipe at the same
    time.
 
+   The :meth:`~Connection.send` method serializes the the object and
+   :meth:`~Connection.recv` re-creates the object.
 
 Synchronization between processes
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -745,6 +748,11 @@ If you use :class:`JoinableQueue` then you **must** call
 semaphore used to count the number of unfinished tasks may eventually overflow,
 raising an exception.
 
+One difference from other Python queue implementations, is that :mod:`multiprocessing`
+queues serializes all objects that are put into them using :mod:`pickle`.
+The object return by the get method is a re-created object that does not share memory
+with the original object.
+
 Note that one can also create a shared queue by using a manager object -- see
 :ref:`multiprocessing-managers`.
 
@@ -811,6 +819,8 @@ For an example of the usage of queues for interprocess communication see
    used for receiving messages and ``conn2`` can only be used for sending
    messages.
 
+   The :meth:`~multiprocessing.Connection.send` method serializes the the object using
+   :mod:`pickle` and the :meth:`~multiprocessing.Connection.recv` re-creates the object.
 
 .. class:: Queue([maxsize])