list分三个组问题python

# 将详细页的内容分成三组，三线程处理
def content_split(**arg_list):
    # 目的将list顺序分组，分成3-4个组把数据写入文件
    try:
        all_list = arg_list.get('all_list_content')
        meta1 = arg_list.get('meta')
        title = arg_list.get('title')
        print(f"meta {arg_list['meta']}")
        print(f'contents size is {len(all_list)}')
        if len(all_list) <= 3:
            write_list(meta1=meta1, title=title, dt=all_list)
            return
        
        res = []
        step = len(all_list) / 3
        last_end = 0
        for i in range(3):
            end_step = step * (i + 1)
            if i == 0:
                # i start end last
                # 0   0     8     8
                # 1    8     16  16
                # 2    16    24  24
                start_step = 0
                res.append(all_list[int(start_step):int(end_step):1])
                last_end = end_step
            else:
                start_step = last_end
                res.append(all_list[int(start_step):int(end_step):1])
                last_end = end_step
                print(f'start_step: {start_step} , end_step:{end_step}, last_end:{last_end} ')
        # 处理落单情况
        if len(all_list) > last_end:
            res.append(all_list[int(last_end)::1])
        # 发起多线程
        print(' res 的len is ', len(res))
        arg_list.pop('all_list_content')
        for dt in res:
            #是为了解决meta问题
            t = threading.Thread(target=write_list, kwargs={'meta1': meta1, 'title': title, 'dt': dt})
            t.start()
            print(f'当前运行的线程是{threading.currentThread().name} is running ')
    except Exception as e:
        print('content split exception-------------')