Steven D'Aprano added the comment: Actually, no, it is a staticmethod. See Guido's tutorial from way back in version 2.2: [quote] __new__ is a static method. When defining it, you don't need to (but may!) use the phrase "__new__ = staticmethod(__new__)", because this is implied by its name (it is special-cased by the class constructor). [end quote] https://www.python.org/download/releases/2.2.3/descrintro I believe that this explains why you have to use this idiom inside __new__ when using super(): def __new__(cls, x): super().__new__(cls, x) If __new__ were a classmethod, the first argument "cls" would be provided automatically. If you try making __new__ a classmethod, it breaks: py> class Test: ... @classmethod ... def __new__(cls): ... pass ... py> x = Test() Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: __new__() takes 1 positional argument but 2 were given whereas a staticmethod works fine. ---------- nosy: +steven.daprano resolution: -> not a bug status: open -> closed _______________________________________ Python tracker http://bugs.python.org/issue21415 _______________________________________

Jurko Gospodnetić added the comment: Thanks for the detailed response! :-( I should have tested more before reporting the issue. Sorry for the noise. :-( I saw the 'cls' argument and assumed it was a class method. Having to explicitly specify cls did not seem to be in contradiction with this since I assumed __new__ is generally invoked on the class directly. I still do not see why it had to be a static method and has not been implemented as a class method, but I guess I'll better ask that kind of a question on the python user's newsgroup. :-) Just in case it can help someone else, here's some sample code what convinced me __new__ was indeed implemented as a static method:

class X: pass X.__new__() # TypeError: object.__new__(): not enough arguments X.__new__(X) # creates a new X instance x = X() x.__new__() # TypeError: object.__new__(): not enough arguments x.__new__(X) # creates a new X instance

If __new__ had been a class method then calling 'x.__new__()' would have worked as well. Thanks again for the replies! Best regards, Jurko Gospodnetić ---------- _______________________________________ Python tracker http://bugs.python.org/issue21415 _______________________________________

Eric Snow added the comment: FYI, __new__() is a staticmethod to accommodate subclassing. Several things that happen at instantiation-time (when __new__() is called), including memory allocation, are tied to the class that is passed in and may be different for subclasses. For example: class Spam(int): def __new__(cls, value): self = super().__new__(Spam, value) self._eggs = 10 return self Spam is passed in instead of int (as would happen if it were a classmethod), resulting in extra memory being allocated for _eggs (and for __dict__ among other things). ---------- nosy: +eric.snow _______________________________________ Python tracker http://bugs.python.org/issue21415 _______________________________________