Add support for numpy buffer format Zf and Zd

Python 3.14 added D and F formats to the ctypes and struct module
Python 3.15 adds D and F formats to the array module and to memoryview

The D and F formats were chosen for compatibility with numpy. Problem: in fact, numpy uses buffer formats Zd and Zf. Example:

>>> import numpy as np
>>> memoryview(np.array([1, 2, 3], dtype='F')).format
'Zf'
>>> memoryview(np.array([1, 2, 3], dtype='D')).format
'Zd'

So I propose adding support for Zd and Zf formats in array, ctypes, memoryview and struct. It requires changing the code expecting a single character to now accept a string (Zd and Zf have 2 characters!).

Linked PRs

pythongh-148675: Add Zd/Zf formats to array, ctypes, memoryview, struct

This issue was escalated to the Steering Council: Decide buffer protocol format string for complex numbers.

The D and F formats were chosen for #132827. Problem: in fact, numpy uses buffer formats Zd and Zf.

In fact, numpy uses both. So, 'F'/'D' codes does make sense for the ctypes module, at least. If SC approves the compatibility break - we can change buffer formats to Zd/Zf in the ctypes module.

So I propose adding support for Zd and Zf formats in array, ctypes, memoryview and struct. It requires changing the code expecting a single character to now accept a string (Zd and Zf have 2 characters!).

I think it's better to revert changes for array and memoryview (#148674) and leave problem for a new champion, who will make a PEP with a proper extension of the struct format string for new types.

gh-148675: Add Zd/Zf formats to array, ctypes, memoryview, struct (#1…

pythongh-148675: Remove F and D formats from array and memoryview

gh-148675: Remove F and D formats from array and memoryview (GH-149368)

Are we all done here for 3.15?

For b1, yes. The Steering Council will need to discuss this, later.

Warn about C API/ABI instability in array.array docs (GH-7669)

Adapt array module declarations Python 3.15 changes (GH-7659)

Warn about C API/ABI instability in array.array docs (GH-7669)

pythongh-148675: Use a string for ctypes cparam tag

gh-148675: Reuse typecodes for array.array() error message (#149779)

gh-148675: Use a string for ctypes cparam tag (#149778)

[3.15] gh-148675: Use a string for ctypes cparam tag (GH-149778) (#14…

Add support for numpy buffer format Zf and Zd

The initial issue has been implemented. For further work, please open new issue. I close this one.

Fix typing of array.typecodes for Python 3.15

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Add support for numpy buffer format `Zf` and `Zd` #148675

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Add support for numpy buffer format Zf and Zd #148675

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vstinner commented on Apr 17, 2026

skirpichev commented on Apr 17, 2026

hugovk commented on May 4, 2026

encukou commented on May 5, 2026

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vstinner commented on May 18, 2026

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Add support for numpy buffer format `Zf` and `Zd` #148675