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How to call C / C++ from Python?

  • Last Updated : 29 Jul, 2020
Geek Week

In order to take advantage of the strength of both languages, developers use Python bindings which allows them to call C/C++ libraries from python.

Now, the question arises that why there is a need for doing this?

  1. As we know that, C has faster execution speed and to overcome the limitation of Global Interpreter Lock(GIL) in python, python bindings are helpful.
  2. We have a large, stable and tested library in C/C++, which will be advantageous to use.
  3. For performing large scale testing of the systems using Python test tools.

Let’s see the C code which we want to execute with Python :


#include <iostream>
class Geek{
        void myFunction(){
            std::cout << "Hello Geek!!!" << std::endl;
int main()
    // Creating an object
    Geek t; 
    // Calling function
    return 0;

We have to provide those cpp declarations as extern “C” because ctypes can only interact with C functions.


extern "C" {
    Geek* Geek_new(){ return new Geek(); }
    void Geek_myFunction(Geek* geek){ geek -> myFunction(); }

Now, compile this code to the shared library :

Finally, write the python wrapper:


# import the module
from ctypes import cdll
# load the library
lib = cdll.LoadLibrary('./')
# create a Geek class
class Geek(object):
    # constructor
    def __init__(self):
        # attribute
        self.obj = lib.Geek_new()
    # define method
    def myFunction(self):
# create a Geek class object
f = Geek()
# object method calling

Output :

Hello Geek!!!

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