threadtest.py

import threading
import time

items = []

lock = threading.Lock() # Shared lock object for our threads.

# Thread work function.
def do_work():
    thread_id = threading.get_ident()

    """
    if lock.locked():
        print(f"Thread {thread_id}: Someone has the lock, no need for me to check the pizza item.")
        return
    """

    print(f"Thread {thread_id} is trying to acquire the lock...")
    print(f"Thread {thread_id} now has the lock.")

    if "Pizza" not in items:
        lock.acquire()  # 1000 threads waiting...

        if "Pizza" not in items:
            print(f"Thread {thread_id} is going to add the 'Pizza'.")
            time.sleep(10)
            items.append("Pizza")
        else:
            print(f"Thread {thread_id} is NOT going to add the 'Pizza'.")
        lock.release()

    print(f"Thread {thread_id} has now released the lock.")

# Spawn 10 threads.
threads = []
for i in range(100):
    thread = threading.Thread(target=do_work)
    thread.start()
    threads.append(thread)

# Wait for all threads to finish.
for t in threads:
    t.join()    # Wait for this thread to finish.

print("All threads have finished, lets see whats in the list.")
print("------------------------------------------------------")

# Lets see whats in the list.
print(items)