gh-105566: Deprecate unusual ways of creating `typing.NamedTuple` classes (#105609)

Deprecate creating a typing.NamedTuple class using keyword arguments to denote the fields (`NT = NamedTuple("NT", x=int, y=str)`). This will be disallowed in Python 3.15. Use the class-based syntax or the functional syntax instead.

Two methods of creating `NamedTuple` classes with 0 fields using the functional syntax are also deprecated, and will be disallowed in Python 3.15: `NT = NamedTuple("NT")` and `NT = NamedTuple("NT", None)`. To create a `NamedTuple` class with 0 fields, either use `class NT(NamedTuple): pass` or `NT = NamedTuple("NT", [])`.

1 files changed, 11 insertions, 0 deletions

diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst
index fcd10e5..cf7c2ca 100644
--- a/Doc/whatsnew/3.13.rst
+++ b/Doc/whatsnew/3.13.rst
@@ -141,6 +141,17 @@ Deprecated
   methods of the :class:`wave.Wave_read` and :class:`wave.Wave_write` classes.
   They will be removed in Python 3.15.
   (Contributed by Victor Stinner in :gh:`105096`.)
+* Creating a :class:`typing.NamedTuple` class using keyword arguments to denote
+  the fields (``NT = NamedTuple("NT", x=int, y=int)``) is deprecated, and will
+  be disallowed in Python 3.15. Use the class-based syntax or the functional
+  syntax instead. (Contributed by Alex Waygood in :gh:`105566`.)
+* When using the functional syntax to create a :class:`typing.NamedTuple`
+  class, failing to pass a value to the 'fields' parameter
+  (``NT = NamedTuple("NT")``) is deprecated. Passing ``None`` to the 'fields'
+  parameter (``NT = NamedTuple("NT", None)``) is also deprecated. Both will be
+  disallowed in Python 3.15. To create a NamedTuple class with 0 fields, use
+  ``class NT(NamedTuple): pass`` or ``NT = NamedTuple("NT", [])``.
+  (Contributed by Alex Waygood in :gh:`105566`.)
 
 * :mod:`array`'s ``'u'`` format code, deprecated in docs since Python 3.3,
   emits :exc:`DeprecationWarning` since 3.13