可以帮我用Python写一个生产者消费者模式的多线程下载程序吗？

当然可以，以下是一个简单的生产者消费者模式的多线程下载程序的Python代码：

import threading
import queue
import requests

class Downloader:
    def __init__(self, url_queue, result_queue):
        self.url_queue = url_queue
        self.result_queue = result_queue

    def download(self):
        while True:
            url = self.url_queue.get()
            try:
                response = requests.get(url)
                self.result_queue.put(response.content)
            except Exception as e:
                print(f"Error downloading {url}: {e}")
            finally:
                self.url_queue.task_done()

class Producer:
    def __init__(self, url_queue, urls):
        self.url_queue = url_queue
        self.urls = urls

    def produce(self):
        for url in self.urls:
            self.url_queue.put(url)

def main():
    urls = [
        "https://www.example.com",
        "https://www.google.com",
        "https://www.python.org",
        "https://www.github.com",
        "https://www.stackoverflow.com"
    ]
    url_queue = queue.Queue()
    result_queue = queue.Queue()
    downloader = Downloader(url_queue, result_queue)
    downloader_threads = [threading.Thread(target=downloader.download) for _ in range(4)]
    producer = Producer(url_queue, urls)
    producer_thread = threading.Thread(target=producer.produce)
    producer_thread.start()
    for downloader_thread in downloader_threads:
        downloader_thread.start()
    url_queue.join()
    while not result_queue.empty():
        result = result_queue.get()
        print(len(result))

if __name__ == "__main__":
    main()

这个程序使用了Python的queue模块来实现生产者消费者模式，其中Downloader类是消费者，Producer类是生产者。程序首先创建了一个包含多个URL的列表，然后创建了一个URL队列和一个结果队列。接着创建了一个Downloader实例和多个Downloader线程，以及一个Producer实例和一个Producer线程。Producer线程将URLs放入URL队列中，Downloader线程从URL队列中取出URL并下载对应的内容，将结果放入结果队列中。最后程序等待URL队列中的所有URL都被处理完毕，然后从结果队列中取出结果并打印结果的长度。