Support zstd from standard library

[ddelange]

Available as stdlib compression.zstd as of python 3.14, with 3.9+ backport at backports.zstd published by the pyzstd maintainer (which got moved into cpython 3.14 standard library).

import example: https://github.com/aio-libs/aiohttp/blob/e260b15ca8d5e3a199cc9db7d0d154b3cb7350d8/aiohttp/compression_utils.py#L25-L28

requirement: backports.zstd==1.0.0 ; python_version < "3.14"

[marcelm]

Yes, that would be great! I thought about this myself when I saw that PEP 784 had been accepted. Maybe something like xopen could even find a place in the new compression module ...

Thanks for the pointer to backports.zstd; I was only aware of the original pyzstd. Using that would be perfect, also allowing us to turn it into a non-optional dependency because the wheel is so much smaller. I don’t want a hard dependency on python-zstandard because the wheels are 8 MB, but backports.zstd wheels are just 500 kB.