如何调用cython cdef（）函数，该函数包含python中的函数作为参数？ [英] How to call a cython cdef() function that contains as a parameter a function in python?

问题描述

我有一个cdef函数，该函数的参数中有一个函数。我正在尝试生成将调用它的python包装器函数。我知道将函数定义为cpdef（）即可访问该函数的python版本。但是，如果这样做，我将得到一个错误（如预期的那样），该错误表示python无法识别我提供的函数定义。

I have a cdef function that has amongst its parameters a function. I am trying to generate a python 'wrapper' function that will call it. I know that defining a function as cpdef() I would be able to get access to a python version of the function. However, if I do this, I will get an error (as expected) that says that python cannot recognize the function definition I provided.

有什么建议吗？

我的原始函数是特定于域的，而且很长，但是我认为下面的示例可以捕获我追求的是什么。我将定义以下 cdef（）函数，

My original function is domain specific and quite long but I think that the following example captures what I am after. I would have the following cdef() function defined,

ctypedef double (*ftype) (double)

cdef cy_myfunc(int a,..., double x, ftype f):
  ...
  cdef double result
  result = f(x)

  return result

定义以下内容，以便我可以在python中调用它：

and I would like to define something like the following so that I can call it in python:

def py_myfunc(a,..., x, f):
    return cy_myfunc(a,...,x,f)

推荐答案

如果您确实需要这样做（可以考虑进行重构，这样就不用了）-您需要某种 PyObject 来存储c函数指针。

If you actually need to this (might think about refactoring so you don't) - you need some kind of PyObject to store the c function pointer.

PyCapsule api提供了一种在python空间中传递不透明指针的方法。可以这样做，我可能缺少一些安全检查

The PyCapsule api provides a way of passing opaque pointers around in python space. Could do something like this, I'm probably missing some safety checks

%%cython
from cpython.pycapsule cimport PyCapsule_New, PyCapsule_GetPointer

ctypedef double (*ftype) (double)

# c function you want to wrapper
cdef double f(double a):
    return a + 22.0

# wrapper capsule
wrapped_f = PyCapsule_New(<void*>f, 'f', NULL)

cdef cy_myfunc(double x, ftype f):
  cdef double result = f(x)
  return result

def py_myfunc(double x, object f_capsule):
    cdef ftype f = <ftype> PyCapsule_GetPointer(f_capsule, 'f')
    return cy_myfunc(x, f)

用法

wrapped_f
# Out[90]: <capsule object "f" at 0x0000000015ACFE70>

py_myfunc(2, wrapped_f)
# Out[91]: 24.0

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