Explain the mechanism of threads in Python and where they can be applied.

In Python, threads are implemented through the threading module. A thread is a separate execution flow within a process, allowing multiple tasks to run in parallel.

However, due to the GIL (Global Interpreter Lock), only one Python code thread executes at a time in the standard CPython implementation, which limits parallelism in CPU-intensive tasks. Nevertheless, threads are useful for I/O-bound tasks (such as network requests, file operations), where the program can wait for an operation to complete and switch between threads.

Example of creating and starting a thread:

import threading

def worker():
    print('Thread has started working')

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

Threads are used to improve application responsiveness, parallelize input/output processing, and implement concurrent tasks.