Guido van Rossum <gu...@python.org> added the comment:
Hm, here's what I measure in Python 3.8.1. (I don't use IPython or notebooks so
this looks a little different.)
>>> timeit.timeit('Foo()', 'class Foo: pass')
0.37630256199999934
>>> timeit.timeit('Foo()', 'class Foo:\n def __new__(cls): return
>>> super().__new__(cls)')
1.5753196039999864
>>> timeit.timeit('Foo()', 'from typing import Generic, TypeVar\nT =
>>> TypeVar("T")\nclass Foo(Generic[T]): pass')
3.8748737150000068
>From this I conclude that adding a minimal __new__() method is responsible for
>about 4x slowdown, and the functionality in typing.py for another factor 2.5.
While this isn't great I don't see an easy way to improve upon this without
rewriting the entire typing module in C. (Some of this may or may not happen
for PEP 604.)
PS. I just realized my Python binary was built with debug options, so absolute
numbers will look different (better) for you -- but relative numbers will look
the same, and I get essentially the same factors with 3.9.0a1+.
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<https://bugs.python.org/issue39168>
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