In what situations is it advisable to use multithreading in a program?

Multithreading in Python is advisable in the following situations:

• When a program performs many input/output operations (such as network requests, file handling), and it is necessary not to block the main thread during waiting.
• To improve the responsiveness of the user interface, so that heavy operations do not block the UI.

However, due to the GIL (Global Interpreter Lock) in standard CPython, multithreading does not speed up CPU-intensive tasks. For such tasks, it is better to use multiprocessing or write extensions in other languages.

An example of using threads for parallel network requests:

import threading
import requests

def fetch_url(url):
    response = requests.get(url)
    print(f"{url}: {len(response.content)} bytes")

threads = []
urls = ["https://example.com", "https://python.org", "https://github.com"]

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

for t in threads:
    t.join()

This approach allows multiple requests to be executed simultaneously without blocking the main thread.