bytes.fromhex() is 1.3 times slower than binascii.a2b_hex()

Bug report

Bug description:

I was looking at modernising some old code that uses binascii.a2b_hex, and I was surprised to find that bytes.fromhex() is a lot slower:

>>> timeit.timeit('bytes.fromhex("abcd1234abcd1234")', number=10000000)
1.0542256180197
>>> timeit.timeit('binascii.a2b_hex("abcd1234abcd1234")', 'import binascii', number=10000000)
0.4072963949292898

I thought maybe it was a difference in the lookup of the bytes classmethod vs the module lookup. It appears that it is, to some extent, but not completely:

>>> timeit.timeit('fromhex("abcd1234abcd1234")', 'fromhex=bytes.fromhex', number=10000000)
0.6133267850382254
>>> timeit.timeit('a2b_hex("abcd1234abcd1234")', 'from binascii import a2b_hex', number=10000000)
0.3788172130007297

Of course, all these times are extremely small, so it probably does not matter in most situations, but still, I found it surprising.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Comece reproduzindo no CPython 3.13/Linux as comparações de timeit de bytes.fromhex() e binascii.a2b_hex() mostradas na issue; em seguida, rastreie os dois pontos de entrada mencionados para entender a origem da diferença. Um resultado útil identificaria se bytes.fromhex() pode ser tornada mais rápida e validaria qualquer alteração com benchmarks equivalentes e testes relevantes.