Call C in Python

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C: build a library

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gcc -c -fPIC libtest.c
gcc -shared libtest.o -o libtest.so

Python: load the library

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from ctypes import *
libtest = cdll.LoadLibrary(libtest.so')
print libtest.func(arg_list)

Makefile sample and python sample code

c_void_p

For the types without need to know the detailed layout, we can just use c_void_p, especially when we cannot find the strictly matched self-defined type such as LP_cfloat_1024.

pointer, POINTER, byref

POINTER is used for defining type.

pointer and byref function similarly. However, pointer does a lot more work since it constructs a real pointer object, so it is faster to use byref if you don’t need the pointer object in Python itself.

memory issue:

write free function in C code

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void freeme(char *ptr)
{
    printf("freeing address: %p\n", ptr);
    free(ptr);
}

call free function in Python

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lib = cdll.LoadLibrary('./string.so')
lib.freeme.argtypes = c_void_p,
lib.freeme.restype = None
lib.freeme(ptr)