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bpo-43923: Add support for generic typing.NamedTuple (#92027)

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Serhiy Storchaka 2022-05-03 01:41:23 +03:00 • committed by GitHub
parent 81fb3548be
commit b04e02c57f
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5 changed files with 66 additions and 4 deletions
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17
Lib/typing.py
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@ -2764,7 +2764,12 @@ _special = frozenset({'__module__', '__name__', '__annotations__'})
class NamedTupleMeta(type):
def __new__(cls, typename, bases, ns):
assert bases[0] is _NamedTuple
assert _NamedTuple in bases
for base in bases:
if base is not _NamedTuple and base is not Generic:
raise TypeError(
'can only inherit from a NamedTuple type and Generic')
bases = tuple(tuple if base is _NamedTuple else base for base in bases)
types = ns.get('__annotations__', {})
default_names = []
for field_name in types:
@ -2778,12 +2783,18 @@ class NamedTupleMeta(type):
nm_tpl = _make_nmtuple(typename, types.items(),
defaults=[ns[n] for n in default_names],
module=ns['__module__'])
nm_tpl.__bases__ = bases
if Generic in bases:
class_getitem = Generic.__class_getitem__.__func__
nm_tpl.__class_getitem__ = classmethod(class_getitem)
# update from user namespace without overriding special namedtuple attributes
for key in ns:
if key in _prohibited:
raise AttributeError("Cannot overwrite NamedTuple attribute " + key)
elif key not in _special and key not in nm_tpl._fields:
setattr(nm_tpl, key, ns[key])
if Generic in bases:
nm_tpl.__init_subclass__()
return nm_tpl
@ -2821,9 +2832,7 @@ def NamedTuple(typename, fields=None, /, **kwargs):
_NamedTuple = type.__new__(NamedTupleMeta, 'NamedTuple', (), {})
def _namedtuple_mro_entries(bases):
if len(bases) > 1:
raise TypeError("Multiple inheritance with NamedTuple is not supported")
assert bases[0] is NamedTuple
assert NamedTuple in bases
return (_NamedTuple,)
NamedTuple.__mro_entries__ = _namedtuple_mro_entries