下载文件

# 在python3下测试import sysimport requestsimport threadingimport datetimeimport time# 传入的命令行参数，要下载文件的urlurl = ""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得到文件主体的大小，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    #  建立一个和要下载文件同样大小的文件    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  # 若是不能整除，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)    # 等待全部线程下载完成    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)