From 33b4d71421be00895d451a6ca286a9225bed980c Mon Sep 17 00:00:00 2001 From: Carl Meyer Date: Wed, 5 Jul 2023 18:12:21 -0600 Subject: [PATCH] gh-105256: What's New note for comprehension over locals() (GH-106378) (cherry picked from commit 13aefd175e3c04529251f175c23cb3ed88451fd0) Co-authored-by: Carl Meyer --- Doc/whatsnew/3.12.rst | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/Doc/whatsnew/3.12.rst b/Doc/whatsnew/3.12.rst index ec13ed57a5c45d..eba3e226fa372c 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`.