CODEWITHSUNDEEP
c++pythonc
Dexter
Dexter

Reputation: 1337

Passing python array to a c function using c_types

I have a wrapper function in C library that interacts with the some python scripts.

int func(uint8_t *_data, int _len);

I want to pass a array or list in python to this function. How to do it ?

Upvotes: 1

Views: 206

Answers (1)

Aya
Aya

Reputation: 41950

The simplest way to create a C array type is to use the multiplication operator on the appropriate type in ctypes, which automatically generates a new type object. For example...

>>> import ctypes
>>> ctypes.c_ubyte * 3
<class '__main__.c_ubyte_Array_3'>

...which can be constructed with the same number of arguments...

>>> (ctypes.c_ubyte * 3)(0, 1, 2)
<__main__.c_ubyte_Array_3 object at 0x7fe51e0fa710>

...or you can use the * operator to call it with the contents of a list...

>>> (ctypes.c_ubyte * 3)(*range(3))
<__main__.c_ubyte_Array_3 object at 0x7fe51e0fa7a0>

...so you'd need something like...

import ctypes

my_c_library = ctypes.CDLL('my_c_library.dll')

def call_my_func(input_list):
    length = len(input_list)
    array = (ctypes.c_ubyte * length)(*input_list)
    return my_c_library.func(array, length)

my_list = [0, 1, 2]
print call_my_func(my_list)

Upvotes: 1

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