Description

JelleZijlstra

opened on Feb 28, 2024

Issue body actions

Feature or enhancement

Proposal:

Currently all of these are allowed:

>>> import ast
>>> ast.expr()
<ast.expr object at 0x10526cce0>
>>> ast.stmt()
<ast.stmt object at 0x1054508d0>
>>> ast.AST()
<ast.AST object at 0x105229610>

But these are meant to be abstract classes; constructing them is not meaningful. I propose to raise a DeprecationWarning when they are constructed and raise an error a few versions down.

(Originally suggested by Cornelius Krupp on discuss.python.)

Has this already been discussed elsewhere?

I have already discussed this feature proposal on Discourse

Links to previous discussion of this feature:

https://discuss.python.org/t/proposed-change-to-ast-node-constructors/46531/4

Linked PRs

• gh-116021: Deprecate support for instantiating abstract AST nodes #137865

Reacted by Kirill Podoprigora and Brian Schubert

Activity

1. JelleZijlstra

   added

   type-featureA feature request or enhancementA feature request or enhancement

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   topic-parser

   on Feb 28, 2024
2. bzoracler commented on Feb 28, 2024

   

   bzoracler

   on Feb 28, 2024

   Contributor

   More actions

   Since there are no current and planned restrictions on subclassing these abstract nodes, I have a gut feeling that deprecating this behaviour will affect code which subclass these abstract nodes and which implicitly or explicitly call the superclass constructor.

   Projects which rely on AST enrichment pipelines (linters, code generators, Python-like language extensions, etc.) may rely on the current behaviour.
3. brianschubert

   added a commit that references this issue on Sep 14, 2025

   Merge branch 'main' into pythongh-116021-ast-depr-abstract

   2f390c8
4. brianschubert

   added a commit that references this issue on Oct 13, 2025

   Merge branch 'main' into pythongh-116021-ast-depr-abstract

   97dbdab
5. brianschubert

   added a commit that references this issue on Nov 22, 2025

   Merge branch 'main' into pythongh-116021-ast-depr-abstract

   f8c0aef
6. brianschubert

   added a commit that references this issue on Apr 28, 2026

   Merge branch 'main' into pythongh-116021-ast-depr-abstract

   0eb074e
7. JelleZijlstra

   added a commit that references this issue on May 2, 2026

   gh-116021: Deprecate support for instantiating abstract AST nodes (#1…

   bdedc4a
8. JelleZijlstra

   closed this as completedon May 2, 2026

Issue actions