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gh-140196: Added constructor behavior changes in ast.rst for python 3.13 #140243

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ambv merged 4 commits into from
Mar 24, 2026
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gh-140196: Added constructor behavior changes in ast.rst for python 3.13 #140243

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gh-140196: Document missing AST node constructor behavior changes in …
MannXo Oct 17, 2025
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Removed the redundant whitespace
MannXo Oct 17, 2025
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ambv Mar 23, 2026
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Merge branch 'main' into gh-140196-doc-ast-3.13
ambv Mar 24, 2026
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gh-140196: Document missing AST node constructor behavior changes in … 
…ast.rst for Python 3.13
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@MannXo
MannXo committed Oct 17, 2025
commit e9a1d23e7120760ae616895d13a34d51ee169528
20 changes: 14 additions & 6 deletions Doc/library/ast.rst
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Expand Up @@ -118,12 +118,12 @@ Node classes
node = ast.UnaryOp(ast.USub(), ast.Constant(5, lineno=0, col_offset=0),
lineno=0, col_offset=0)

If a field that is optional in the grammar is omitted from the constructor,
it defaults to ``None``. If a list field is omitted, it defaults to the empty
list. If a field of type :class:`!ast.expr_context` is omitted, it defaults to
:class:`Load() <ast.Load>`. If any other field is omitted, a :exc:`DeprecationWarning` is raised
and the AST node will not have this field. In Python 3.15, this condition will
raise an error.
If a field that is optional in the grammar is omitted from the constructor,
it defaults to ``None``. If a list field is omitted, it defaults to the empty
list. If a field of type :class:`!ast.expr_context` is omitted, it defaults to
:class:`Load() <ast.Load>`. If any other field is omitted, a :exc:`DeprecationWarning` is raised
and the AST node will not have this field. In Python 3.15, this condition will
raise an error.

.. versionchanged:: 3.8

Expand All @@ -134,6 +134,14 @@ Node classes
Simple indices are represented by their value, extended slices are
represented as tuples.

.. versionchanged:: 3.13

AST node constructors were changed to provide sensible defaults for omitted
fields: optional fields now default to ``None``, list fields default to an
empty list, and fields of type :class:`ast.expr_context` default to
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:class:`Load() <ast.Load>`. Previously, omitted attributes would not exist on constructed
nodes (accessing them raised :exc:`AttributeError`).

.. versionchanged:: 3.14

The :meth:`~object.__repr__` output of :class:`~ast.AST` nodes includes
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