diff options
Diffstat (limited to 'Doc')
| -rw-r--r-- | Doc/library/ast.rst | 25 | ||||
| -rw-r--r-- | Doc/whatsnew/3.13.rst | 15 |
2 files changed, 29 insertions, 11 deletions
diff --git a/Doc/library/ast.rst b/Doc/library/ast.rst index c943c2f..d629393 100644 --- a/Doc/library/ast.rst +++ b/Doc/library/ast.rst @@ -103,20 +103,15 @@ Node classes For example, to create and populate an :class:`ast.UnaryOp` node, you could use :: - node = ast.UnaryOp() - node.op = ast.USub() - node.operand = ast.Constant() - node.operand.value = 5 - node.operand.lineno = 0 - node.operand.col_offset = 0 - node.lineno = 0 - node.col_offset = 0 - - or the more compact :: - 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 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 Class :class:`ast.Constant` is now used for all constants. @@ -140,6 +135,14 @@ Node classes In the meantime, instantiating them will return an instance of a different class. +.. deprecated-removed:: 3.13 3.15 + + Previous versions of Python allowed the creation of AST nodes that were missing + required fields. Similarly, AST node constructors allowed arbitrary keyword + arguments that were set as attributes of the AST node, even if they did not + match any of the fields of the AST node. This behavior is deprecated and will + be removed in Python 3.15. + .. note:: The descriptions of the specific node classes displayed here were initially adapted from the fantastic `Green Tree diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst index ca5a0e7..3a277d7 100644 --- a/Doc/whatsnew/3.13.rst +++ b/Doc/whatsnew/3.13.rst @@ -206,6 +206,21 @@ array ast --- +* The constructors of node types in the :mod:`ast` module are now stricter + in the arguments they accept, and have more intuitive behaviour when + arguments are omitted. + + If an optional field on an AST node is not included as an argument when + constructing an instance, the field will now be set to ``None``. Similarly, + if a list field is omitted, that field will now be set to an empty list. + (Previously, in both cases, the attribute would be missing on the newly + constructed AST node instance.) + + If other arguments are omitted, a :exc:`DeprecationWarning` is emitted. + This will cause an exception in Python 3.15. Similarly, passing a keyword + argument that does not map to a field on the AST node is now deprecated, + and will raise an exception in Python 3.15. + * :func:`ast.parse` now accepts an optional argument ``optimize`` which is passed on to the :func:`compile` built-in. This makes it possible to obtain an optimized ``AST``. |