PyQt6 uses PySequence_Fast() which was removed from the limited C API 3.14

Bug report

Bug description:

In the issue #91417 I removed PySequence_Fast(), commit 2ad069d:

Remove PySequence_Fast() from the limited C API. The function never worked with the limited C API. It was added by mistake.

Problem: PyQt6 uses the function! I propose to add back PySequence_Fast() to the limited C API.

PyQt6:

./qpy/QtOpenGL/qpyopengl_attribute_array.cpp:    values = PySequence_Fast(values, "an attribute array must be a sequence");
./qpy/QtOpenGL/qpyopengl_attribute_array.cpp:            itm = PySequence_Fast(itm,
./qpy/QtOpenGL/qpyopengl_uniform_value_array.cpp:    values = PySequence_Fast(values,
./qpy/QtOpenGL/qpyopengl_uniform_value_array.cpp:            itm = PySequence_Fast(itm,
./qpy/QtOpenGL/qpyopengl_value_array.cpp:    PyObject *seq = PySequence_Fast(values,

They reimplemented PySequence_Fast_GET_SIZE() and PySequence_Fast_GET_ITEM() macros which don't work with the limited C API:

// Replacements for the corresponding Python macros that use the limited API.
#define Sequence_Fast_Size(o) \
    (PyList_Check(o) ? PyList_Size(o) : PyTuple_Size(o))
#define Sequence_Fast_GetItem(o, i)\
    (PyList_Check(o) ? PyList_GetItem(o, i) : PyTuple_GetItem(o, i))

CPython versions tested on:

3.14

Operating systems tested on:

Linux

Linked PRs

gh-130947: Add again PySequence_Fast() to the limited C API #130948

Fedora downstream issue: https://bugzilla.redhat.com/show_bug.cgi?id=2345504

pythongh-130947: Add again PySequence_Fast() to the limited C API

Can PyQt6 project can add an #ifdef to avoid a conflict? The Py... is supposed to be ours and not for downstream users.

Also, +1 for adding back PySequence_Fast(). I've found it to be pretty useful. Presumably the PyQt maintainers also found it to be so useful that they had to reimplement it.

Can PyQt6 project can add an #ifdef to avoid a conflict? The Py... is supposed to be ours and not for downstream users.

Which conflict? PyQt6 defines Sequence_Fast_Size() and Sequence_Fast_GetItem() macros: without Py prefix.

pythongh-130947: Add again PySequence_Fast() to the limited C API

gh-130947: Add again PySequence_Fast() to the limited C API (#130948)

I added back PySequence_Fast() in the limited C API: 10cbd1f.

pythongh-130947: Add again PySequence_Fast() to the limited C API (py…

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PyQt6 uses PySequence_Fast() which was removed from the limited C API 3.14 #130947

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PyQt6 uses PySequence_Fast() which was removed from the limited C API 3.14 #130947

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Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

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vstinner commented on Mar 7, 2025

rhettinger commented on Mar 7, 2025

vstinner commented on Mar 7, 2025

vstinner commented on Mar 13, 2025

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