下载文件

# 在python3下测试

import sys
import requests
import threading
import datetime
import time

# 传入的命令行参数，要下载文件的url
url = ""


def Handler(start, end, url, filename):
    headers = {'Range': 'bytes=%d-%d' % (start, end)}
    r = requests.get(url, headers=headers, stream=True)

    # 写入文件对应位置
    with open(filename, "r+b") as fp:
        fp.seek(start)
        var = fp.tell()
        fp.write(r.content)
        fp.close()
    print(start,end)


def download_file(url, num_thread=5):
    r = requests.head(url)
    try:
        file_name = url.split('/')[-1]
        file_size = int(
            r.headers['content-length'])  # Content-Length获得文件主体的大小，当http服务器使用Connection:keep-alive时，不支持Content-Length
    except:
        print("检查URL，或不支持对线程下载")
        return

    #  创建一个和要下载文件一样大小的文件
    print("create file")
    fp = open("D:\HOTA\UpdateBasePackage.zip", "w")
    fp.truncate(file_size)
    fp.close()
    time.sleep(5)

    # 启动多线程写文件
    num_thread = 100
    part = file_size // num_thread  # 如果不能整除，最后一块应该多几个字节
    # num_thread = 10
    # part = 100*1024*1024
    tempList=[]
    for i in range(num_thread):
        start = part * i
        if i == num_thread - 1:  # 最后一块
            end = file_size
        else:
            end = start + part
        temp = [start,end]
        tempList.append(temp)
    print(tempList)
    tag = 0
    runningThread = []
    while True:
        if len(runningThread)<5:
            t = threading.Thread(target=Handler, kwargs={'start': tempList[tag][0], 'end': tempList[tag][1], 'url': url,
                                                         'filename': "D:\HOTA\UpdateBasePackage.zip"})
            # t.setDaemon(True)
            t.start()
            runningThread.append(t)
            tag = tag + 1
            if tag == 100:
                break
        for t in runningThread:
            if not t.isAlive():
                runningThread.remove(t)
                t.join()
        print(runningThread)
        time.sleep(1)


    # 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)


if __name__ == '__main__':
    start = datetime.datetime.now().replace(microsecond=0)
    download_file(url)
    end = datetime.datetime.now().replace(microsecond=0)
    print("用时: ", end='')
    print(end - start)