示例：

#!/usr/bin/env python3

-*- coding:utf-8 -*-

@Time: 2020/12/16 10:42

@Author:zhangmingda

@File: urllib_multi_download.py

@Software: PyCharm

Description: 使用urllib 模块 实现多线程下载某个文件测试

from concurrent.futures import ThreadPoolExecutor, as_completed
from urllib.request import urlopen
from urllib.request import Request
from urllib.request import quote
import json
import math
import os

class DownLoader(object):
def __init__(self):
self.part_size = 1024 * 1024 * 10 # 分块下载大小
self.part_thread_num = 10
self.BUFFER_SIZE = 64 * 1024

def download\_part(self, encode\_url, part\_filename, offset, end\_bytes):  
    """  
    :param encode\_url:经过URL编码的网络地址  
    :param part\_filename: 文件块儿名字  
    :param offset: 下载字节起始点(包含)  
    :param end\_bytes: 下载字节结束点(包含)  
    :return: (下载结果)  
    """  
    # 构造请求头  
    range\_header = {  
        'Range': 'bytes=%s-%s' % (offset, end\_bytes)  
    }  
    print(range\_header)  
    cur\_task\_ret = False  
    expected\_file\_size = end\_bytes - offset + 1  
    part\_req = Request(encode\_url,headers=range\_header)  
    with open(part\_filename, 'wb') as local\_part\_fd:  
        with urlopen(part\_req) as req\_fd:  
            while True:  
                # 一直从网络读数据  
                data = req\_fd.read(self.BUFFER\_SIZE)  
                if not data:  
                    break  
                local\_part\_fd.write(data)  
    if expected\_file\_size == os.stat(part\_filename).st\_size:  
        print('%s 与预期块儿文件大小相符' % part\_filename)  
        cur\_task\_ret = True  
        # break  
    else:  
        print('%s 与预期块儿文件大小 不符,预期%s字节,实际得到%s 字节' % (  
        part\_filename, expected\_file\_size, os.stat(part\_filename).st\_size))

    return {part\_filename: cur\_task\_ret}

def download(self, url):  
    finally\_filename = os.path.basename(url)  
    # 将URL编码成%字符串格式  
    encode\_url = quote(url, safe=";/?:@&=+$,")  
    print(encode\_url)  
    # 构造请求  
    req = Request(encode\_url)  
    # 发起请求并且获取内容长度  
    with urlopen(req) as fp:  
        # print(json.dumps(dir(fp),indent=1))  
        print(fp.getheaders())  
        # length = fp.getheader('content-Range')  
        length = fp.getheader('Content-Length')  
        length = int(length)  
        print(type(length))  
        print('length:', length)

    # 分块任务列表  
    thread\_list = \[\]  
    # 每个块儿下载的结果  
    multi\_chunk\_download\_result = {}  
    chunk\_size = self.part\_size  
    # 计算需要下载的块儿个数  
    chunk\_count = int(math.ceil(length / float(chunk\_size)))  
    pool\_args\_list = \[\]

    # 计算每个块儿请求的字节范围  
    for i in range(chunk\_count):  
        offset = chunk\_size \* i  
        end\_bytes = min(chunk\_size \* (i + 1), length) - 1  
        # 将一个文件划分的所有块儿任务，添加到任务列表  
        part\_num = i + 1  
        part\_filename = finally\_filename + '.' + str(part\_num)  
        # 每个块儿请求的范围，块儿名字，加到线程参数列表  
        pool\_args\_list.append((encode\_url, part\_filename, offset, end\_bytes))

    # \*\*\*\*\*\*\*\*开始多线程下载数据，并获取下载结果\*\*\*\*\*\*\*\*\*\*\*\*\*\*  
    # 构建线程池实例  
    tp = ThreadPoolExecutor(max\_workers=self.part\_thread\_num)  
    # 全部添加到任务队列开始处理  
    \[thread\_list.append(tp.submit(self.download\_part, \*args)) for args in pool\_args\_list\]  
    # 等待所有线程结束，获取全部线程的执行结果  
    \[multi\_chunk\_download\_result.update(part\_thread.result()) for part\_thread in as\_completed(thread\_list)\]

    # 下载总结  
    print('下载总结')  
    # 如果任务数和块儿数对不上，报一下出入  
    if len(multi\_chunk\_download\_result) != chunk\_count:  
        raise RuntimeError(  
            "%s part miss,expect=%d,actual=%d" % (finally\_filename, chunk\_count, len(multi\_chunk\_download\_result)))  
    # 如果任务都完毕，检查是否有失败的块儿  
    for item in multi\_chunk\_download\_result.keys():  
        if not multi\_chunk\_download\_result\[item\]:  
            raise RuntimeError("%s part upload has fail" % item)  
    # 都OK 整合文件  
    with open(finally\_filename, 'wb') as local\_fd:  
        for i in range(chunk\_count):  
            part\_filename = finally\_filename + '.' + str(i + 1)  
            with open(part\_filename, 'rb') as part\_fd:  
                while True:  
                    bytes\_data = part\_fd.read(self.BUFFER\_SIZE)  
                    if not bytes\_data:  
                        break  
                    local\_fd.write(bytes\_data)

    if length == os.stat(finally\_filename).st\_size:  
        print('%s  下载完成，文件大小相符' % finally\_filename)  
        for part\_filename in multi\_chunk\_download\_result.keys():  
            os.remove(part\_filename)  
    else:  
        print('%s  下载完成，但大小不符,content\_length:%s  下载后大小 %s' % (finally\_filename, length,os.stat(finally\_filename).st\_size ))

if __name__ == '__main__':
downloader = DownLoader()
url = 'https://ks3-cn-beijing.ksyun.com/zhangmingda/111-3333333.Python安装与命令行操作.mp4'
print(url)
downloader.download(url)