Python 实现多线程分块下载

有时候需要使用Python下载一个比较大的文件，我们利用Python的多线程Threading来完成，然后根据文件大小分配线程和每个线程的文件大小。

def Handler(start, end, url, filename):
    headers = {'Range': 'bytes=%d-%d' % (start, end)}
    with requests.get(url, headers=headers,stream=True) as r:
        with open(filename, "r+b") as fp:
            fp.seek(start)
            var = fp.tell()
            fp.write(r.content)
def download(url,tittle, num_thread = 10):
    r = requests.head(url)
    try:
        file_name = tittle
        file_size = int(r.headers['content-length'])
    except:
        print("检查URL，或不支持对线程下载")
        return
    fp = open(file_name, "wb")
    fp.truncate(file_size)
    fp.close()
    part = file_size // num_thread
    for i in range(num_thread):
        start = part * i
        if i == num_thread - 1:
            end = file_size
        else:
            end = start + part
        t = threading.Thread(target=Handler, kwargs={'start': start, 'end': end, 'url': url, 'filename': file_name})
        t.setDaemon(True)
        t.start()
 
# 等待所有线程下载完成
main_thread = threading.current_thread()
for t in threading.enumerate():
    if t is main_thread:
        continue
    t.join()
print('%s 下载完成' % file_name)