kylehounslow/wrap_python_cpp_example

Simple example of compiling C++ shared library (.so file) and wrapping with Python

wrap_python_cpp_example

Simple example of compiling C++ shared library (.so file) and wrapping with Python.
In this example we use g++ and python3 on a Unix system.

Step 1 - Compiling C++

Generate a file file.cpp containing the following:

#include <iostream>
using namespace std;

extern "C" // makes C++ functions accessible
{

int my_function(int arg){
	cout<<"In C++ my_function. You passed me: "<<arg<<endl;
	return arg*2;
}

} // end extern "C"

Compile object file (.o) from .cpp file

g++ -c -Wall -Werror -fPIC file.cpp -o file.o

Generate shared library file (.so)

g++ file.o -shared -o libfile.so

Your directory structure should now look like:

└── my_folder/
    ├── file.cpp
    ├── file.o
    └── libfile.so

Step 2 - Wrapping with Python

Generate a file file.py containing the following:

import ctypes

# load shared library file
c_lib = ctypes.CDLL("./libfile.so")
# now we can access the functions defined within `extern "C"{}`
a = c_lib.my_function(21)
print("a = {}".format(a))

Your directory structure should now look like:

└── my_folder/
    ├── file.cpp
    ├── file.o
    └── file.py
    └── libfile.so
    

Execute the Python file

python file.py

output:

In C++ my_function. You passed me: 21
a = 42