How is multithreading implemented in Python and how is it related to execution threads?

In Python, multithreading is implemented using the threading module, which allows creating and managing execution threads.

Each thread is a separate line of code execution that can run in parallel with others.

However, due to the GIL (Global Interpreter Lock) in the standard CPython implementation, only one Python code thread executes at a time, which limits real parallelism in computations. Nevertheless, multithreading is useful for I/O-bound tasks, where threads can wait for operations to complete without blocking the main thread.

Example of creating a thread:

import threading

def worker():
    print("Thread has started")

thread = threading.Thread(target=worker)
thread.start()
thread.join()  # Wait for the thread to finish

Thus, execution threads are separate sequences of execution, and multithreading in Python is a way to organize multiple such sequences, although due to GIL, they do not always execute simultaneously.