BUG: preserve top-level subarray dtypes in dtype_to_descr#31291
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wuxian08 wants to merge 5 commits intonumpy:mainfrom
Open
BUG: preserve top-level subarray dtypes in dtype_to_descr#31291wuxian08 wants to merge 5 commits intonumpy:mainfrom
wuxian08 wants to merge 5 commits intonumpy:mainfrom
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added 5 commits
April 20, 2026 08:52
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This PR addresses #31280.
It makes two related changes in numpy.lib.format:
dtype_to_descrnow preserves top-level subarray dtypes, sodtype_to_descranddescr_to_dtyperound-trip those dtypes correctly.open_memmap(..., mode='w+')now normalizes top-level subarray dtypes when writing .npy headers by recursively folding subarray dimensions into the array shape and writing the base dtype in descr.The tests were extended to cover:
dtype_to_descr/descr_to_dtypeopen_memmaproundtrips for user-specified subarray dtypesFirst time committer introduction
I am a C++ and Python developer, and we use NumPy heavily for data processing and for data exchange between C++ and Python (using pybind11). This issue came up while we were looking for a reliable way to serialize and deserialize NumPy dtypes.
AI Disclosure
I used Codex CLI during the preparation of this PR. It helped inspect the relevant NumPy code, suggest code changes and tests, and help me reason through edge cases. I reviewed the code myself, made additional changes manually, and I am submitting this PR myself.