Documentation

In Python 3.13, AST node constructors now provide defaults for the omitted fields:

• Optional fields: default toNone
• List fields: default to an empty list
• expr_context fields: default toLoad()

Previously in Python 3.12 and earlier, these omitted fields would not exist as attributes, causingAttributeError when accessed.

These information can be found inWhat’s New In Python 3.13, but not in theast documentation itself.

Since this is a significant behavioral change, it should be documented in theast module documentation with a.. versionchanged:: 3.13 directive.

Linked PRs

• gh-140196: Added constructor behavior changes in ast.rst for python 3.13 #140243
• [3.14] gh-140196: Added constructor behavior changes in ast.rst for python 3.13 (GH-140243) #146351
• [3.13] gh-140196: Added constructor behavior changes in ast.rst for python 3.13 (GH-140243) #146354