From: Carl Meyer <carl@oddbird.net>
Date: Thu, 6 Jul 2023 00:12:21 +0000 (-0600)
Subject: gh-105256: What's New note for comprehension over locals() (#106378)
X-Git-Tag: v3.13.0a1~1502
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=13aefd175e3c04529251f175c23cb3ed88451fd0;p=thirdparty%2FPython%2Fcpython.git

gh-105256: What's New note for comprehension over locals() (#106378)
---

diff --git a/Doc/whatsnew/3.12.rst b/Doc/whatsnew/3.12.rst
index 1af80ea62b39..a892f92dd262 100644
--- a/Doc/whatsnew/3.12.rst
+++ b/Doc/whatsnew/3.12.rst
@@ -253,6 +253,12 @@ Inlining does result in a few visible behavior changes:
 * Calling :func:`locals` inside a comprehension now includes variables
   from outside the comprehension, and no longer includes the synthetic ``.0``
   variable for the comprehension "argument".
+* A comprehension iterating directly over ``locals()`` (e.g. ``[k for k in
+  locals()]``) may see "RuntimeError: dictionary changed size during iteration"
+  when run under tracing (e.g. code coverage measurement). This is the same
+  behavior already seen in e.g. ``for k in locals():``. To avoid the error, first
+  create a list of keys to iterate over: ``keys = list(locals()); [k for k in
+  keys]``.
 
 Contributed by Carl Meyer and Vladimir Matveev in :pep:`709`.