How to Call a Python Script from C

Integrating Python scripts with C programs can be incredibly useful, especially when you want to leverage Python's rich ecosystem while maintaining the performance benefits of C. In this guide, we'll explore the most popular and widely used method to achieve this.

---

Why Call Python from C?

There are several reasons you might want to call a Python script from a C program:

• To use Python libraries that don't have C equivalents.
• To prototype functionality quickly in Python before implementing it in C.
• To automate tasks where Python's scripting capabilities are more convenient.

---

Using Python's C API

The most robust way to call Python from C is by using Python's C API, which allows direct embedding of the Python interpreter into your C program.

Step 1: Include Python Headers

First, ensure you have Python development headers installed. Then include them in your C code:

#include <Python.h>

Step 2: Initialize the Python Interpreter

Before calling any Python code, you must initialize the interpreter:

Py_Initialize();

Step 3: Run a Python Script

You can execute a Python script using PyRun_SimpleFile():

FILE* file = fopen("script.py", "r");
PyRun_SimpleFile(file, "script.py");
fclose(file);

Step 4: Clean Up

Always finalize the interpreter when done:

Py_Finalize();

---

Calling Specific Python Functions

If you need to call a specific Python function from C, follow these steps:

1. Import the Python module.
2. Get a reference to the function.
3. Call the function with arguments.

Here's an example:

// Import the module
PyObject* module = PyImport_ImportModule("example");

// Get the function
PyObject* func = PyObject_GetAttrString(module, "add_numbers");

// Call the function with arguments
PyObject* args = PyTuple_Pack(2, PyLong_FromLong(5), PyLong_FromLong(10));
PyObject* result = PyObject_CallObject(func, args);

// Convert result to C type
long sum = PyLong_AsLong(result);

// Clean up
Py_DECREF(module);
Py_DECREF(func);
Py_DECREF(args);
Py_DECREF(result);

---

Compiling the C Program

When compiling, link against Python's library. For example, with GCC:

gcc -o program program.c $(python3-config --cflags --ldflags)

---

Summary: This guide explains how to call Python scripts from C using Python's C API, covering basic execution and function calls. The method is widely used for integrating Python's flexibility with C's performance.

Incoming search terms
- How to call Python script from C program
- Best way to run Python code in C
- Python C API tutorial for beginners
- Embedding Python in C application
- How to execute Python function from C
- Python.h example usage in C
- Compile C program with Python integration
- Passing arguments from C to Python function
- How to use PyRun_SimpleFile in C
- Python and C integration guide
- Calling Python modules from C code