Annotation-based decorator for `ctypes` function pointers · Issue #153903 · python/cpython · GitHub

Feature or enhancement

Proposal:

The idea is to add a decorator that extracts type annotations and a name for a function signature, and then use that information to generate argtypes and restype for a _CFuncPtr object. For example:

@wrap_dll_function(ctypes.pythonapi)
def PyObject_GetAttrString(op: ctypes.py_object, attr: ctypes.c_char_p) -> ctypes.py_object:
    ...

See #104533 for prior work.

Has this already been discussed elsewhere?

I have already discussed this feature proposal on Discourse

Links to previous discussion of this feature:

https://discuss.python.org/t/annotation-based-sugar-for-ctypes/26579

Linked PRs

gh-153903: Add a `ctypes` decorator for generating function pointers …

pythongh-153903: Fix ctypes wrap_dll_function() with string annotations

gh-153903: Fix ctypes wrap_dll_function() with string annotations (#1…

gh-153903: Use `@ctypes.util.wrap_dll_function()` with pythonapi (#15…

gh-153903: Use `@ctypes.util.wrap_dll_function()` (#154122)

It would also be nice if this propagated doc comments, which I don't believe gh-153904 does

Do you have a compelling use case for that?

It would just be a nice-to-have if things like help() in the REPL (or ? in ipython) reproduced the docstring if one was provided on the stub. I think this could also be used by tools like sphinx. Whenever I write a decorator I tend to use functools.wraps, but I think the only relevant thing here is actually the .__doc__ member.

Currently, if you use the example in the docs:

import ctypes
from ctypes.util import wrap_dll_function

@wrap_dll_function(ctypes.pythonapi)
def PyObject_GetAttrString(op: ctypes.py_object, attr: ctypes.c_char_p) -> ctypes.py_object:
   pass

help(PyObject_GetAttrString) would print the help for ctypes._FuncPtr. It would be nice if a user could write something like

@wrap_dll_function(ctypes.pythonapi)
def PyObject_GetAttrString(op: ctypes.py_object, attr: ctypes.c_char_p) -> ctypes.py_object:
   """Calls the internal ..."""
   pass

And have that string not just be swallowed/ignored

Seems reasonable. Would you like to submit a PR?

Happy to!

gh-153903: Copy docstrings and other metadata in `ctypes.util.wrap_dl…

pythongh-153903: Copy docstrings and other metadata in `ctypes.util.w…

Annotation-based decorator for `ctypes` function pointers · Issue #153903 · python/cpython · GitHub

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Annotation-based decorator for ctypes function pointers #153903

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Annotation-based decorator for `ctypes` function pointers · Issue #153903 · python/cpython · GitHub

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Annotation-based decorator for ctypes function pointers #153903

Description

Feature or enhancement

Proposal:

Has this already been discussed elsewhere?

Links to previous discussion of this feature:

Linked PRs

Activity

WardBrian commented on Jul 21, 2026

ZeroIntensity commented on Jul 21, 2026

WardBrian commented on Jul 21, 2026

ZeroIntensity commented on Jul 21, 2026

WardBrian commented on Jul 21, 2026

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