请帮我修改此段代码 def crawling(url): global net net.url = url urls = net.get_url() return urls def Pool(urls): with ThreadPoolExecutor(max_workers=4) as crawl: n_urls = [] for url in urls: n_url = crawl.submit(crawling, url) n_urls.append(n_url) new_urls = [] for n_url in n_urls: new_urls.extend(n_url.result()) return new_urls 改变后实现的功能一样

修改后的代码如下：

def crawling(url):
    return net.get_url(url)

def Pool(urls):
    with ThreadPoolExecutor(max_workers=4) as crawl:
        results = crawl.map(crawling, urls)
        new_urls = []
        for result in results:
            new_urls.extend(result)
        return new_urls

这里使用了 `ThreadPoolExecutor` 的 `map` 方法，可以将任务分配给线程池中的多个线程进行并行处理，最终将结果合并。这样可以更加简洁地实现任务并行处理，并且避免了使用 `submit` 和 `result` 方法时可能出现的阻塞问题。