What is a thread and how is multithreading implemented in Python?

A thread is a unit of execution within a process that can run concurrently with other threads, sharing the process's memory.

In Python, multithreading is implemented using the threading module. However, due to the GIL (Global Interpreter Lock), only one thread executes Python bytecode at a time in the standard CPython implementation, which limits parallelism in CPU-bound tasks.

Nevertheless, multithreading is useful for I/O-bound tasks (e.g., network requests, file operations), where threads can wait for I/O operations to complete, allowing other threads to run.

Example of creating and starting a thread:

import threading

def worker():
    print('Thread is running')

thread = threading.Thread(target=worker)
thread.start()
thread.join()

For CPU-bound tasks in Python, it is better to use multiprocessing (multiprocessing) to bypass the GIL limitation.