__class__ not set in typing.NamedTuple #85795
Comments
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This is likely related or a dupe of https://bugs.python.org/issue29270, but the error message is different. I'm posting this to confirm it's the same issue, or not, and to at least provide a google result for people who also see this error as 29270 seems to imply this might not be fixable. Like 29270, it involves the fact that the interpreter seems to be looking at my super() call inside of a method without actually calling it, and then getting ups 8000 et about __classcell__: from typing import NamedTuple
class X(NamedTuple):
a: str
b: str
# comment this out to remove the issue
def foo(self):
return super(X, self)and that's it! on my interpreter: Python 3.8.3 (default, May 23 2020, 16:34:37) I get: $ python test3.py
Traceback (most recent call last):
File "test3.py", line 4, in <module>
class X(NamedTuple):
RuntimeError: __class__ not set defining 'X' as <class '__main__.X'>. Was __classcell__ propagated to type.__new__?The most surprising thing is that this seems extremely basic and google is not finding this error message for me. |
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The example used to raise deprecation warning in python 3.7 python3.7 -Wall ../backups/bpo41629.py It was converted into RuntimeError in f5e7b19 . Related https://bugs.python.org/issue23722 |
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I just stumbled across this issue trying to resolve this: https://bugs.python.org/issue42765? While this fails: from typing import NamedTuple
class Spamm(NamedTuple): def __getitem__(self, index_or_key):
"""Returns the respective item."""
if isinstance(index_or_key, str):
try:
return getattr(self, index_or_key)
except AttributeError:
raise IndexError(index_or_key) from None
return super().__getitem__(index_or_key)
def keys(self):
return self._fields
def main():
spamm = Spamm(12, 'hello')
print(dir(spamm))
print(spamm._fields)
d = dict(spamm)
print(d)
if __name__ == '__main__':
main()with Traceback (most recent call last):
File "/home/neumann/test.py", line 4, in <module>
class Spamm(NamedTuple):
RuntimeError: __class__ not set defining 'Spamm' as <class '__main__.Spamm'>. Was __classcell__ propagated to type.__new__?The following works: from typing import NamedTuple
def _getitem(instance, index_or_key):
"""Returns the respective item."""
if isinstance(index_or_key, str):
try:
return getattr(instance, index_or_key)
except AttributeError:
raise IndexError(index_or_key) from None
return super().__getitem__(index_or_key)
def dicttuple(cls: tuple):
"""Extends a tuple class with methods for the dict constructor."""
cls.keys = lambda self: self._fields
cls.__getitem__ = _getitem
return cls
@dicttuple
class Spamm(NamedTuple):def main():
spamm = Spamm(12, 'hello')
print(dir(spamm))
print(spamm._fields)
d = dict(spamm)
print(d)
if __name__ == '__main__':
main()And produces: ['__add__', '__annotations__', '__class__', '__class_getitem__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__module__', '__mul__', '__ne__', '__new__', '__orig_bases__', '__reduce__', '__reduce_ex__', '__repr__', '__rmul__', '__setattr__', '__sizeof__', '__slots__', '__str__', '__subclasshook__', '_asdict', '_field_defaults', '_fields', '_make', '_replace', 'bar', 'count', 'foo', 'index', 'keys'] I am a bit baffled, why it works when the method is injected via a decorator. |
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I met this issue in Python 3.10 too. |
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This issue is still present in Python 3.11.2. The super function cannot be used within a named tuple or a |
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In gh-129352, we drew a conclusion that it is unnecessary for typed named tuples to support It may be a good idea to detect and prevent the use of |
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Sure, type checkers (or linters: detecting this issue doesn't really need a full type checker) could detect this. I don't think it's especially common, but tool maintainers may be willing to entertain contributions. |
….NamedTuple` subclasses (python#130082)
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typing.NamedTuple__classcell__bug, support overriding__repr__easily #129344super()inNamedTuplesubclasses #129352super()is used intyping.NamedTuplesubclasses #130082The text was updated successfully, but these errors were encountered: