Concurrent programming in Python: Multithreading vs. Multiprocessing

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In the realm of Python programming, understanding concurrent execution mechanisms like multithreading and multiprocessing is crucial for optimizing performance, especially in applications that require heavy computation or I/O operations. This guide elucidates the differences between these two approaches and provides real-world use cases for each.

Understanding Multithreading and Multiprocessing


Multithreading involves running multiple threads (smaller units of a process) concurrently. It’s ideal for I/O-bound tasks where the program waits for external responses. In Python, the Global Interpreter Lock (GIL) means that threads are not truly executed in parallel but are useful for I/O-bound tasks.


Multiprocessing, on the other hand, involves running multiple processes concurrently. Each process has its own memory space and Python interpreter. It’s suitable for CPU-bound tasks that require heavy computation and can benefit from parallel execution on multiple cores.

Make sure Python is installed on your system. Both multithreading and multiprocessing are part of Python’s standard library, so no additional installation is needed.

Multithreading example: Web scraper

A web scraper that fetches data from multiple URLs simultaneously is a perfect use case for multithreading due to its I/O-bound nature.

import threading
import requests
def fetch_url(url):
    print(f"Fetching {url}")
    response = requests.get(url)
    print(f"Finished fetching {url}")
urls = ["", "", ""]
threads = []
for url in urls:
    thread = threading.Thread(target=fetch_url, args=(url,))
for thread in threads:

Multiprocessing example: Data processing

For CPU-bound tasks like processing a large dataset, multiprocessing can significantly reduce execution time.

from multiprocessing import Pool
def process_data(data):
    # Some CPU-intensive processing
    return data * data

if __name__ == "__main__":
    pool = Pool(processes=4)
    data = [1, 2, 3, 4, 5]
    results =, data)
For multithreading, run the web scraper script to see how multiple URLs are fetched concurrently. For multiprocessing, execute the data processing script to observe how the dataset is processed in parallel.
Author: user