在 Python 中使用 ctypes 将指针传递给 C 函数的结构指针

Question

In a C library there's:

typedef struct A *  B;
int create_b(B* b);

and using ctypes I need the Python equivalent to:

B b;
create_b(&b)

The struct A is implemented in Python as class A(ctypes.Structure) .

So, I tried:

b = ctypes.POINTER(A)
lib.create_b(ctypes.byref(b))

but it's not working. There are many similar questions, but none I tried helped.

Answer 1

This line

b = ctypes.POINTER(A)

is just setting b to refer to the same type ctypes.POINTER(A) , where what is really wanted is a variable constructed with that type. The line is missing the parentheses at the end:

b = ctypes.POINTER(A)()