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ModuleNotFoundError: No module named 'crc32c' #3592
Description
Zarr version
v3.1.3
Numcodecs version
v0.16.4
Python Version
3.13
Operating System
Linux
Installation
Using uv into virtual environment
Description
The just released numcodecs removes the crc32 dependency in favour of the google-crc32c library, but codecs/crc32c_.py in the latest pip release 3.1.3 requires crc32c.py on line 8. Obviously this is fixed in main, but it means that pip install zarr won't produce a working zarr install.
Steps to reproduce
# /// script
# requires-python = ">=3.11"
# dependencies = [
# "zarr==3.1.3",
# ]
# ///
#
from zarr.codecs import crc32c_Additional output
No response
Activity
d-v-b commentedon Nov 20, 2025
thanks for this report, and sorry for the breakage! I'm going to get a zarr-python release out ASAP that should fix the problem of a broken pip install. For older versions of zarr-python we may need to consider reverting dropping crc32c from numcodecs.
d-v-b commentedon Nov 20, 2025
see zarr-developers/numcodecs#801
jhamman commentedon Nov 20, 2025
@lispandfound - are you able to install
crc32cto your environment directly?lispandfound commentedon Nov 20, 2025
I certainly can do this, and it does resolve the issue when I do. The main problem with this approach is that the crash occurs in automated testing workflows so I'd have to issue updates to all those repositories to fix the issue downstream. I'm not in a huge rush, so I would rather just wait for this issue to be resolved than update it.
d-v-b commentedon Nov 20, 2025
IMO the best solution is something that doesn't require users to manually change their dependency declaration. I think the only way to achieve that is with a rapid release of a new version of numcodecs that fixes this problem.
d-v-b commentedon Nov 20, 2025
see zarr-developers/numcodecs#802. If we merge these changes and issue a numcodecs
0.16.5release the breakage will be fixed. @zarr-developers/python-core-devs please look into this, or a comparable solution.maxrjones commentedon Nov 21, 2025
Thanks again for the quick bug report! This was fixed in zarr by #3515 and in numcodecs (for earlier zarr versions) in zarr-developers/numcodecs#802.
d-v-b commentedon Nov 21, 2025
I opened #3597 as part of the post-mortem for this issue
circumvent zarr-developers/zarr-python#3592