How to Call a Python Script Using C++

Integrating Python scripts into a C++ application can be a powerful way to leverage Python's simplicity and extensive libraries while maintaining the performance benefits of C++. This guide will walk you through the most popular and efficient methods to achieve this.

Method 1: Using the Python/C API

The Python/C API is the most direct way to call Python from C++. It allows you to embed Python interpreter within your C++ code.

Step 1: Include Python Headers

First, ensure Python development libraries are installed. Then, include the Python header in your C++ code:

#include <Python.h>

Step 2: Initialize the Python Interpreter

Before calling any Python code, initialise the interpreter:

Py_Initialize();

Step 3: Run a Python Script

Use PyRun_SimpleString to execute Python code:

PyRun_SimpleString("print('Hello from Python!')");

Step 4: Clean Up

Always finalise the interpreter when done:

Py_Finalize();

Method 2: Using System Calls

For simpler use cases, you can execute a Python script as a subprocess using C++ system calls.

Using `system()` Function

Call the Python script directly:

#include <cstdlib>
int main() {
    system("python3 script.py");
    return 0;
}

Using `popen()` for Output Handling

To capture Python script output in C++:

FILE* pipe = popen("python3 script.py", "r");
if (!pipe) return -1;
char buffer[128];
while (fgets(buffer, sizeof(buffer), pipe) {
    printf("%s", buffer);
}
pclose(pipe);

Method 3: Using Boost.Python

Boost.Python is a popular library for seamless C++ and Python integration.

Step 1: Install Boost.Python

Install Boost libraries with Python support:

sudo apt-get install libboost-python-dev

Step 2: Write a C++ Wrapper

Example of embedding Python:

#include <boost/python.hpp>
int main() {
    Py_Initialize();
    boost::python::exec("print('Boost.Python says hello!')");
    Py_Finalize();
    return 0;
}

Best Practices

Use error handling (PyErr_Print()) when using Python/C API.
For performance-critical applications, prefer Boost.Python.
For simple scripts, system calls are easier to implement.

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