For which use cases is the multithreading module in Python designed?

The multithreading module in Python (threading) is designed for scenarios where tasks related to input/output (I/O-bound) need to be executed in parallel, such as:

• Handling network requests
• Reading and writing files
• Interacting with databases
• Waiting for responses from external services

Due to the GIL, multithreading is inefficient for CPU-bound tasks (heavy computations), as threads do not execute in parallel on multiple cores. For such tasks, multiprocessing is a better choice.

Example of using threading for parallel file downloading:

import threading
import requests

def download(url):
    resp = requests.get(url)
    print(f"Downloaded {url} with {len(resp.content)} bytes")

urls = ["http://example.com/file1", "http://example.com/file2"]
threads = []

for url in urls:
    t = threading.Thread(target=download, args=(url,))
    t.start()
    threads.append(t)

for t in threads:
    t.join()