怎样在Python中实现多线程？

import threading
import time

def task(name):
    print(f"Task {name} started")
    time.sleep(2)
    print(f"Task {name} finished")

thread = threading.Thread(target=task, args=("A",))
thread.start()
thread.join()

print("Main thread finished")

import threading
import queue
import time

def worker(q):
    while True:
        item = q.get()
        if item is None:
            break
        print(f"Processing {item}")
        time.sleep(1)
        q.task_done()

q = queue.Queue()

num_threads = 3
for i in range(num_threads):
    t = threading.Thread(target=worker, args=(q,))
    t.start()

for item in ['A', 'B', 'C', 'D', 'E']:
    q.put(item)

q.join()

for i in range(num_threads):
    q.put(None)

print("All tasks completed")

import threading

class Counter:
    def __init__(self):
        self.count = 0
        self.lock = threading.Lock()

    def increment(self):
        with self.lock:
            self.count += 1

    def get_count(self):
        with self.lock:
            return self.count

counter = Counter()

def worker():
    for _ in range(100000):
        counter.increment()

threads = []
for _ in range(10):
    t = threading.Thread(target=worker)
    threads.append(t)
    t.start()

for t in threads:
    t.join()

print(f"Final count: {counter.get_count()}")

from concurrent.futures import ThreadPoolExecutor
import time

def task(name):
    print(f"Task {name} started")
    time.sleep(2)
    print(f"Task {name} finished")

with ThreadPoolExecutor(max_workers=3) as executor:
    futures = [executor.submit(task, f"Task-{i}") for i in range(5)]

for future in futures:
    future.result()

print("All tasks completed")