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dstansby opened this issue Apr 3, 2025 · 4 comments · May be fixed by #3068
Open

Array.read_only incorrect #2949

dstansby opened this issue Apr 3, 2025 · 4 comments · May be fixed by #3068
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bug Potential issues with the zarr-python library

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@dstansby
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dstansby commented Apr 3, 2025 

import zarr
import zarr.storage

store = zarr.storage.MemoryStore()
zarr.create((100,), store=store, zarr_format=2, path="a")


arr = zarr.open_array(store=store, path="a", zarr_format=2, mode="r")
print(arr.read_only)
# False

Given the mode is "r", I think .read_only should return True?
@d-v-b
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d-v-b commented Apr 3, 2025 •
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In zarr-python 3, arrays and groups don't have their own read / write permission model, instead all of that is handled by the storage layer.

Thus the read_only property was added for backwards compatibility with v2, and it doesn't do what you would expect -- it reports whether the array is backed by a read-only store.. So in your example, because you are re-using a store instance, it keeps its original mode (which is probably a). I agree that this is confusing.

@dstansby
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dstansby commented Apr 3, 2025

Hmm, in that case should passing a mode to open_array raise an exception, when the passed mode is different to the mode the store is open with?

@d-v-b
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d-v-b commented Apr 3, 2025

i believe open_array has a mode parameter for backwards compatibility reasons. Since we are controlling access modes with the storage layer, IMO it doesn't make sense to pretend that it's also controlled by the array / group layer, and we should deprecate the mode keyword argument.

@dstansby
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dstansby commented Apr 3, 2025

we should deprecate the mode keyword argument.

👍 - I think it's pretty bad that it silently does nothing at the moment!

This was referenced May 1, 2025
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@dstansby dstansby added the bug Potential issues with the zarr-python library label May 18, 2025
@dstansby dstansby added this to the 3.0.8 milestone May 18, 2025
@dstansby dstansby linked a pull request May 18, 2025 that will close this issue
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@dstansby dstansby removed this from the 3.0.8 milestone May 19, 2025
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Error on invalid store mode dstansby/zarr-python
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