python 多线程下载

好的，针对你的问题，我可以给出以下的代码示例：

import requests
import threading
def download(url, start_pos, end_pos, file):
    headers = {'Range': 'bytes=%d-%d' % (start_pos, end_pos)}
    res = requests.get(url, headers=headers)
    file.seek(start_pos)
    file.write(res.content)

def multi_thread_download(url, num_thread=8):
    res = requests.head(url)
    file_name = url.split('/')[-1]
    file_size = int(res.headers['Content-Length'])
    part = file_size // num_thread
    file = open(file_name, 'wb')
    threads = []
    for i in range(num_thread):
        start_pos = i * part
        if i == num_thread - 1:
            end_pos = file_size
        else:
            end_pos = start_pos + part - 1
        t = threading.Thread(target=download, args=(url, start_pos, end_pos, file))
        threads.append(t)
        t.start()
    for t in threads:
        t.join()
    file.close()

multi_thread_download('http://example.com/example.zip', num_thread=8)

这个代码示例实现了一个多线程下载文件的功能。首先通过 `requests.head` 方法获取文件大小，然后根据线程数将文件分成若干个部分，每个线程下载一个部分。最后将所有部分合并成一个完整的文件。