What are semaphores in Python threading?

Can you explain what semaphores are in Python threading?

Sure! Semaphores are synchronization primitives that control access to a shared resource in a concurrent environment.

How do semaphores differ from mutexes?

Semaphores allow a certain number of threads to access a resource, while mutexes allow only one thread at a time.

Can you give me a code example of using semaphores?

Absolutely! Here's a simple example:

import threading
import time

semaphore = threading.Semaphore(2)

def access_resource(thread_id):
    with semaphore:
        print(f'Thread {thread_id} is accessing the resource.')
        time.sleep(2)
        print(f'Thread {thread_id} has released the resource.')

threads = [threading.Thread(target=access_resource, args=(i,)) for i in range(5)]
for thread in threads:
    thread.start()
for thread in threads:
    thread.join()

What happens if a thread tries to acquire a semaphore that is already at its limit?

The thread will block and wait until a semaphore is released by another thread, allowing it to proceed.