I use the standard strategy of writing to a temporary file in the same directory, and then renaming it to the desired name. This ensure that Zarr writes are either complete or not written at all.

It would be nice if partial writes (_put() withstart) could also be atomic, but I'm honestly not sure if both atomic and efficient partial writes of files are possible. Interestingly, I don't see any uses ofset_partial_values() inside Zarr, so maybe this feature isn't needed after all? (see#2859 for discussion)

TODO:

Add unit tests and/or doctests in docstrings
Changes documented as a new file inchanges/
GitHub Actions have all passed
Test coverage is 100% (Codecov passes)

Use atomic writes in LocalStore

3d991f0

Fixeszarr-developers#3411I use the standard strategy of writing to a temporary file in the samedirectory, and then renaming it to the desired name.This ensure that Zarr writes are either complete or not written at all.

github-actionsbot added the needs release notesAutomatically applied to PRs which haven't added release notes label

Aug 27, 2025

shoyer changed the title~~Use atomic writes in LocalStore~~Use atomic writes for new files in LocalStore

Aug 27, 2025

shoyer added2 commits

August 27, 2025 14:21

Lint fixes

fb1f32d

import sort

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codecovbot commentedAug 27, 2025•
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Codecov Report

❌ Patch coverage is91.66667% with2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.70%. Comparing base (c9509ee) to head (f2c1fcd).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/zarr/storage/_local.py	91.66%	2 Missing⚠️

Additional details and impacted files

@@            Coverage Diff             @@##             main    #3412      +/-   ##==========================================- Coverage   94.70%   94.70%   -0.01%==========================================  Files          79       79                Lines        9532     9549      +17     ==========================================+ Hits         9027     9043      +16- Misses        505      506       +1

Files with missing lines	Coverage Δ
src/zarr/storage/_local.py	`92.39% <91.66%> (+0.17%)`	⬆️

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shoyer added2 commits

August 27, 2025 15:35

actually fix import order

cfc01e1

ruff format

03dc6f4

d-v-b reviewed

Aug 28, 2025

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src/zarr/storage/_local.py

		)->int\|None:
		path.parent.mkdir(parents=True,exist_ok=True)
		# write takes any object supporting the buffer protocol
		view=value.as_buffer_like()

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d-v-bAug 28, 2025

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this makes me wonder whyBuffer doesn't implement the buffer protocol!

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Aug 28, 2025

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we should probably get arelease note for this change. I'm happy to write one if that works. Otherwise it looks g2g!

Add release note

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github-actionsbot removed the needs release notesAutomatically applied to PRs which haven't added release notes label

Aug 28, 2025

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d-v-benabled auto-merge (squash)

August 28, 2025 17:26

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shoyer commentedAug 28, 2025

The missing code coverage is for the unused/untestedset_partial_values (#2859) and foros.rename on Windows (I guess Codecov does not include the Windows build?)