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May 11, 2025
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gh-133817: remove keyword argument syntax for NamedTuple objects #133822

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12 changes: 8 additions & 4 deletions Doc/whatsnew/3.15.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -118,10 +118,14 @@ Deprecated
Removed
=======

module_name
-----------

* TODO
typing
------

* The undocumented keyword argument syntax for creating
:class:`~typing.NamedTuple` classes (for example,
``Point = NamedTuple("Point", x=int, y=int)``).
Use the class-based syntax or the functional syntax instead.
(Contributed by Bénédikt Tran in :gh:`133817`.)


Porting to Python 3.15
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95 changes: 22 additions & 73 deletions Lib/test/test_typing.py
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Expand Up @@ -8080,78 +8080,13 @@ class Group(NamedTuple):
self.assertIs(type(a), Group)
self.assertEqual(a, (1, [2]))

def test_namedtuple_keyword_usage(self):
with self.assertWarnsRegex(
DeprecationWarning,
"Creating NamedTuple classes using keyword arguments is deprecated"
):
LocalEmployee = NamedTuple("LocalEmployee", name=str, age=int)

nick = LocalEmployee('Nick', 25)
self.assertIsInstance(nick, tuple)
self.assertEqual(nick.name, 'Nick')
self.assertEqual(LocalEmployee.__name__, 'LocalEmployee')
self.assertEqual(LocalEmployee._fields, ('name', 'age'))
self.assertEqual(LocalEmployee.__annotations__, dict(name=str, age=int))

with self.assertRaisesRegex(
TypeError,
"Either list of fields or keywords can be provided to NamedTuple, not both"
):
NamedTuple('Name', [('x', int)], y=str)

with self.assertRaisesRegex(
TypeError,
"Either list of fields or keywords can be provided to NamedTuple, not both"
):
NamedTuple('Name', [], y=str)

with self.assertRaisesRegex(
TypeError,
(
r"Cannot pass `None` as the 'fields' parameter "
r"and also specify fields using keyword arguments"
)
):
NamedTuple('Name', None, x=int)

def test_namedtuple_special_keyword_names(self):
with self.assertWarnsRegex(
DeprecationWarning,
"Creating NamedTuple classes using keyword arguments is deprecated"
):
NT = NamedTuple("NT", cls=type, self=object, typename=str, fields=list)

self.assertEqual(NT.__name__, 'NT')
self.assertEqual(NT._fields, ('cls', 'self', 'typename', 'fields'))
a = NT(cls=str, self=42, typename='foo', fields=[('bar', tuple)])
self.assertEqual(a.cls, str)
self.assertEqual(a.self, 42)
self.assertEqual(a.typename, 'foo')
self.assertEqual(a.fields, [('bar', tuple)])

def test_empty_namedtuple(self):
expected_warning = re.escape(
"Failing to pass a value for the 'fields' parameter is deprecated "
"and will be disallowed in Python 3.15. "
"To create a NamedTuple class with 0 fields "
"using the functional syntax, "
"pass an empty list, e.g. `NT1 = NamedTuple('NT1', [])`."
)
with self.assertWarnsRegex(DeprecationWarning, fr"^{expected_warning}$"):
NT1 = NamedTuple('NT1')

expected_warning = re.escape(
"Passing `None` as the 'fields' parameter is deprecated "
"and will be disallowed in Python 3.15. "
"To create a NamedTuple class with 0 fields "
"using the functional syntax, "
"pass an empty list, e.g. `NT2 = NamedTuple('NT2', [])`."
)
with self.assertWarnsRegex(DeprecationWarning, fr"^{expected_warning}$"):
NT2 = NamedTuple('NT2', None)
with self.assertRaisesRegex(TypeError, "missing.*required.*argument"):
BAD = NamedTuple('BAD')

NT3 = NamedTuple('NT2', [])
NT1 = NamedTuple('NT1', {})
NT2 = NamedTuple('NT2', ())
NT3 = NamedTuple('NT3', [])

class CNT(NamedTuple):
pass # empty body
Expand All @@ -8166,16 +8101,18 @@ class CNT(NamedTuple):
def test_namedtuple_errors(self):
with self.assertRaises(TypeError):
NamedTuple.__new__()
with self.assertRaisesRegex(TypeError, "object is not iterable"):
NamedTuple('Name', None)

with self.assertRaisesRegex(
TypeError,
"missing 1 required positional argument"
"missing 2 required positional arguments"
):
NamedTuple()

with self.assertRaisesRegex(
TypeError,
"takes from 1 to 2 positional arguments but 3 were given"
"takes 2 positional arguments but 3 were given"
):
NamedTuple('Emp', [('name', str)], None)

Expand All @@ -8187,10 +8124,22 @@ def test_namedtuple_errors(self):

with self.assertRaisesRegex(
TypeError,
"missing 1 required positional argument: 'typename'"
"got some positional-only arguments passed as keyword arguments"
):
NamedTuple(typename='Emp', name=str, id=int)

with self.assertRaisesRegex(
TypeError,
"got an unexpected keyword argument"
):
NamedTuple('Name', [('x', int)], y=str)

with self.assertRaisesRegex(
TypeError,
"got an unexpected keyword argument"
):
NamedTuple('Name', [], y=str)

def test_copy_and_pickle(self):
global Emp # pickle wants to reference the class by name
Emp = NamedTuple('Emp', [('name', str), ('cool', int)])
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41 changes: 1 addition & 40 deletions Lib/typing.py
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Expand Up @@ -2968,7 +2968,7 @@ def annotate(format):
return nm_tpl


def NamedTuple(typename, fields=_sentinel, /, **kwargs):
def NamedTuple(typename, fields, /):
"""Typed version of namedtuple.

Usage::
Expand All @@ -2988,48 +2988,9 @@ class Employee(NamedTuple):

Employee = NamedTuple('Employee', [('name', str), ('id', int)])
"""
if fields is _sentinel:
if kwargs:
deprecated_thing = "Creating NamedTuple classes using keyword arguments"
deprecation_msg = (
"{name} is deprecated and will be disallowed in Python {remove}. "
"Use the class-based or functional syntax instead."
)
else:
deprecated_thing = "Failing to pass a value for the 'fields' parameter"
example = f"`{typename} = NamedTuple({typename!r}, [])`"
deprecation_msg = (
"{name} is deprecated and will be disallowed in Python {remove}. "
"To create a NamedTuple class with 0 fields "
"using the functional syntax, "
"pass an empty list, e.g. "
) + example + "."
elif fields is None:
if kwargs:
raise TypeError(
"Cannot pass `None` as the 'fields' parameter "
"and also specify fields using keyword arguments"
)
else:
deprecated_thing = "Passing `None` as the 'fields' parameter"
example = f"`{typename} = NamedTuple({typename!r}, [])`"
deprecation_msg = (
"{name} is deprecated and will be disallowed in Python {remove}. "
"To create a NamedTuple class with 0 fields "
"using the functional syntax, "
"pass an empty list, e.g. "
) + example + "."
elif kwargs:
raise TypeError("Either list of fields or keywords"
" can be provided to NamedTuple, not both")
if fields is _sentinel or fields is None:
import warnings
warnings._deprecated(deprecated_thing, message=deprecation_msg, remove=(3, 15))
fields = kwargs.items()
types = {n: _type_check(t, f"field {n} annotation must be a type")
for n, t in fields}
field_names = [n for n, _ in fields]

nt = _make_nmtuple(typename, field_names, _make_eager_annotate(types), module=_caller())
nt.__orig_bases__ = (NamedTuple,)
return nt
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2025-05-10-12-07-54.gh-issue-133817.4GMtKV.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Remove support for creating :class:`~typing.NamedTuple` classes via the
undocumented keyword argument syntax. Patch by Bénédikt Tran.
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