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Inconsistent () indexing/size behavior from v2->v3 #2713
Description
Zarr version
v3.0.0
Numcodecs version
0.14.1
Python Version
3.12
Operating System
Mac
Installation
uv
Description
Previously something like z[()] where z is a () shape array would return a scalar and now returns a one-elem array e.g., np.array(1) instead of np.float64(1.0)
Steps to reproduce
v3:
import numpy as np
import zarr
z = zarr.open_group('foo.zarr')
z.create_array("bar", dtype=float, shape=())
z["bar"][...] = np.array(1) # why doesn't [:] work?
z["bar"][()] # arrayv2:
import numpy as np
import zarr
z = zarr.open_group('foo.zarr')
z.create_dataset("bar", dtype=float, shape=(), data=np.array(1))
z["bar"][()] # np.floatAdditional output
No response
Reacted by Davis Bennett
Activity
[-]Inconsisten `()` indexing/size behavior from v2->v3[/-][+]Inconsistent `()` indexing/size behavior from v2->v3[/+]jhamman commentedon Jan 15, 2025
Thanks @ilan-gold for the report. Looks like we missed the
()indexer in #2583brokkoli71 commentedon Jan 15, 2025
I'll take a look at it.
regarding your comment in:
z["bar"][...] = np.array(1) # why doesn't [:] work?The semantics of
[:]is "select everything in the first dimension". I think since we have 0 dimensions this is expected to fail because there is no first dimension.ilan-gold commentedon Jan 16, 2025
Makes sense!
brokkoli71 commentedon Jan 16, 2025
Do we want to return scalars when accessing zero-dimensional arrays? This would mean that the return value of
__getitem__is no longer NDArrayLike and may make typing more difficultdstansby commentedon Jan 16, 2025
Returning a scalar here would be consistent with numpy (2.2.1):