And what do you think about imposing a hard limit on Python integers, so integers larger than$2^{2^{63}-1}-1$ or$2^{2^{64}-1}-1$ could not even be created? Then the number of bits can always be expressed as a 64-bit integer, error checks after_PyLong_NumBits and_PyLong_Frexp can be removed, and the code for shift operations andint.bit_count() significantly simplified.

I can update this PR for the later idea or implement it in a separate issue.

And what do you think about imposing a hard limit on Python integers ...

That sounds totally reasonable to me (presumably as a CPython detail, rather than an aspect of Python-the-language). Any future computing landscape that makes operating on ints of that size remotely feasible is going to lookvery different from today's landscape.

Thanks,@gpshead.