From 51ec70db2deed0497969e747dd9c8ce95e8d37b9 Mon Sep 17 00:00:00 2001 From: Hood Chatham Date: Mon, 20 May 2024 13:42:15 -0400 Subject: [PATCH] DOCS: Suggest always calling exec with a globals argument and no locals argument (GH-119235) Many users think they want a locals argument for various reasons but they do not understand that it makes code be treated as a class definition. They do not want their code treated as a class definition and get surprised. The reason not to pass locals specifically is that the following code raises a `NameError`: ```py exec(""" def f(): print("hi") f() def g(): f() g() """, {}, {}) ``` The reason not to leave out globals is as follows: ```py def t(): exec(""" def f(): print("hi") f() def g(): f() g() """) ``` (cherry picked from commit 7e1a130b8ff1ed8b3a5f00fe0f06d3916b852216) Co-authored-by: Hood Chatham --- Doc/library/functions.rst | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst index b314cb2a703993..d8f65b06763cad 100644 --- a/Doc/library/functions.rst +++ b/Doc/library/functions.rst @@ -604,9 +604,13 @@ are always available. They are listed here in alphabetical order. will be used for both the global and the local variables. If *globals* and *locals* are given, they are used for the global and local variables, respectively. If provided, *locals* can be any mapping object. Remember - that at the module level, globals and locals are the same dictionary. If exec - gets two separate objects as *globals* and *locals*, the code will be - executed as if it were embedded in a class definition. + that at the module level, globals and locals are the same dictionary. + + .. note:: + + Most users should just pass a *globals* argument and never *locals*. + If exec gets two separate objects as *globals* and *locals*, the code + will be executed as if it were embedded in a class definition. If the *globals* dictionary does not contain a value for the key ``__builtins__``, a reference to the dictionary of the built-in module