This is evident when we look at classes in Python, which are a mixture of these two languages’ class mechanisms.
However, writing a Python interface in C can provide additional speed and performance that pure Python code may not be able to achieve. By using the power of C, we can call system calls or use certain C library functions that aren’t available in pure Python. This tutorial will guide you through the process of creating a simple wrapper for the fputs() C library function using the Python API with Cython.
To get started, create a new directory called “my_c_module” and navigate into it:
# Create a new directory called "my_c_module"
mkdir my_c_module
# Navigate into the newly created directory
cd my_c_module/
# The above two commands can be combined into one using the && operator
# This ensures that the second command is only executed if the first one is successful
# Create a new directory called "my_c_module" and navigate into it
mkdir my_c_module && cd my_c_module/
Next, let’s initialize our project with Git:
# This script initializes a Git repository in the current directory.
# The "git init" command is used to create a new Git repository.
# The "." at the end specifies the current directory as the location for the repository.
#!/bin/bash
git init # Initialize a new Git repository
. # Specify the current directory as the location for the repository
Now that we have a clean slate to work with, let’s create a new file called setup.py in the root directory of our project using your favorite text editor or IDE:
# Importing the setup function from the setuptools module
from setuptools import setup
# Setting up the setup function with the necessary arguments
setup(
# Defining the name of the module
name='my_c_module',
# Defining the version of the module
version='0.1'
)
This creates a basic setup script that we’ll use to build and install our Python interface in C later on. The name of the module is “my_c_module” and the current version is 0.1 (you can change this if you want).
Now, let’s create another file called my_c_module.h in a new directory called src:
# This script creates a new directory called "src" and navigates into it
mkdir src && cd src/
# This command creates a new file called "my_c_module.h" in the "src" directory
touch my_c_module.h
Inside the newly created my_c_module.h file, add the following code:
// This is a header file for a C module called "my_c_module"
// It is used to declare the function "fputs" and its parameters
#ifndef MY_C_MODULE_H // This is a preprocessor directive that checks if the header file has already been included
#define MY_C_MODULE_H // If not, it defines the header file to avoid multiple inclusions
// This is the function declaration for "fputs"
// It takes in a string (const char*) and a file stream (FILE*) as parameters
int fputs(const char *str, FILE *stream);
#endif // MY_C_MODULE_H // This ends the preprocessor directive and closes the header file
This defines a new function called “fputs” that takes two arguments: a string and a file stream. This is the same signature as the original C library function we’re wrapping!
Now, let’s create another file called my_c_module.c in the src directory:
# This script creates a new file called my_c_module.c in the src directory
# by using the touch command.
# The touch command creates a new file if it doesn't exist, or updates the timestamp of an existing file.
# First, we define a new function called "fputs" that takes two arguments: a string and a file stream.
# This function is used to write a string to a file.
# The function signature is the same as the original C library function we're wrapping.
# Next, we create the file my_c_module.c in the src directory using the touch command.
touch src/my_c_module.c
Inside this new file, add the following code:
// This script includes the necessary libraries and header files for the code to run properly.
// The <stdio.h> library is used for input/output operations, while "my_c_module.h" is a custom header file.
#include <stdio.h>
#include "my_c_module.h"
// This function takes in a string and a file stream as parameters.
// It uses the fprintf function to write the string to the specified file stream.
// The return value is the number of characters written to the file.
int fputs(const char *str, FILE *stream) {
return fprintf(stream, "%s", str);
}
// The main function is the entry point of the program.
int main() {
// This line calls the fputs function and passes in a string and the standard output stream (stdout).
// The string "Hello World!" will be written to the console.
fputs("Hello World!", stdout);
// This line calls the custom function from the "my_c_module.h" header file.
// The function will print out a custom message to the console.
custom_function();
// The return statement ends the program and returns a value of 0 to indicate successful execution.
return 0;
}
This defines the actual implementation of our wrapper function using the original C library function we’re wrapping!
Now that we have all the necessary files in place, let’s go back to setup.py and add some more code:
# This script imports necessary modules for setting up the wrapper function
from setuptools import setup # Importing the setup function from setuptools module
import os # Importing the os module for file operations
from distutils.extension import Extension # Importing the Extension class from distutils.extension module
from Cython.Build import cythonize # Importing the cythonize function from Cython.Build module
# This creates a list of Extension objects, specifying the name and source file for the wrapper function
ext_modules = [Extension("my_c_module", ["src/my_c_module.c"])] # Creating an Extension object with name "my_c_module" and source file "src/my_c_module.c"
# This sets up the package with the specified name, version, and extension modules
setup(name='my_c_module', version='0.1', ext_modules=cythonize(ext_modules)) # Setting up the package with name "my_c_module", version "0.1", and extension modules created using the cythonize function
This adds some new code to our setup script that tells setuptools how to build and install our Python interface in C using Cython! The “src/my_c_module.c” argument specifies the location of our wrapper function, which is defined inside my_c_module.h.
Can you please provide more information on how to use this module once it’s installed?