import sys,time

 for i in range():

     sys.stdout.write("#")

     sys.stdout.flush()

     time.sleep(0.1)

 #sys.stdout.write ,表示写到标准输出（屏幕）

    sys.stdout.flush ,表示每写一个字符就立刻把内存缓冲区的内容刷出来

    time模块--time.sleep， 表示休眠时间

    def progress_bar(self, ret_size, total_size):

        '''

        显示进度条

        ret_size: 已经传输的数据大小

        total_size: 文件的总大小

        '''

        percent_num = int(float(ret_size) / float(total_size) * )

        chr_num = int(percent_num / ) * '*'

        if percent_num == :

            per_str = '\r{0}M/{1}M {2}% : {3}\n'.format(int(ret_size / ),

                                                        int(total_size / ),

                                                        percent_num,

                                                        chr_num)

        else:

            per_str = '\r{0}M/{1}M {2}% : {3}'.format(int(ret_size / ),

                                                      int(total_size / ),

                                                      percent_num,

                                                      chr_num)

        print(per_str, end='', flush=True)