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bpo-36517: Raise error on multiple inheritance with NamedTuple #19363

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Merged
merged 2 commits into from
Apr 4, 2020
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bpo-36517: Raise error on multiple inheritance with NamedTuple #19363

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46cb614
bpo-36517: Raise error on multiple inharitence with NamedTuple.
serhiy-storchaka Apr 4, 2020
b7e45e1
Update Misc/NEWS.d/next/Library/2020-04-04-17-49-39.bpo-36517.Ilj1IJ.rst
serhiy-storchaka Apr 4, 2020
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7 changes: 7 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3626,6 +3626,13 @@ def _source(self):
return 'no chance for this as well'
""")

def test_multiple_inheritance(self):
class A:
pass
with self.assertRaises(TypeError):
class X(NamedTuple, A):
x: int

def test_namedtuple_keyword_usage(self):
LocalEmployee = NamedTuple("LocalEmployee", name=str, age=int)
nick = LocalEmployee('Nick', 25)
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3 changes: 3 additions & 0 deletions Lib/typing.py
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Expand Up @@ -1728,6 +1728,9 @@ class NamedTupleMeta(type):
def __new__(cls, typename, bases, ns):
if ns.get('_root', False):
return super().__new__(cls, typename, bases, ns)
if len(bases) > 1:
raise TypeError("Multiple inheritance with NamedTuple is not supported")
assert bases[0] is NamedTuple
types = ns.get('__annotations__', {})
nm_tpl = _make_nmtuple(typename, types.items())
defaults = []
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2020-04-04-17-49-39.bpo-36517.Ilj1IJ.rst
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@@ -0,0 +1,2 @@
Multiple inheritance with :class:`typing.NamedTuple` now raises an error
instead of silently ignoring other types.