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ValueError: No Zarr data type found that matches dtype 'dtype('uint32')' on Windows #3796
Description
Zarr version
3.15
Numcodecs version
0.14.1
Python Version
3.13
Operating System
Windows
Installation
using poetry into virtual environment
Description
On Windows, the following snippet, which worked with zarr 2, fails with zarr 3 with
ValueError: No Zarr data type found that matches dtype 'dtype('uint32')'
Repro:
import zarr
a = np.array([1, 2], dtype=np.uint32) & 1
zarr.array(a)The issue seems to be that the dtype is UIntDtype instead of UInt32Dtype.
When running the following snippet:
dtypes = [
(np.array([1, 2], dtype=np.uint16) & 1).dtype,
(np.array([1, 2], dtype=np.uint32) & 1).dtype,
(np.array([1, 2], dtype=np.uint64) & 1).dtype,
]
for dtype in dtypes:
print(f"{dtype} {type(dtype)}")we get
uint16 <class 'numpy.dtypes.UInt16DType'>
uint32 <class 'numpy.dtypes.UIntDtype'>
uint64 <class 'numpy.dtypes.UInt64DType'>
Steps to reproduce
import zarr
a = np.array([1, 2], dtype=np.uint32) & 1
zarr.array(a)Additional output
No response
Activity
d-v-b commentedon Mar 20, 2026
thanks for this report! The fix is probably to robustly figure out which numpy int data type is actually a 32 bit integer.
fix zarr-developers#3796: Handle generic dtype instances in dtype mat…