B站top100视频属于哪个分区，为什么有时爬出来是99个，有时是100个？

zoning_list = []
all_zoning = ['动画','音乐','舞蹈','知识','生活','时尚','娱乐','放映厅','美食','单机游戏',
              '番剧','国创','游戏','数码','鬼畜','资讯','影视','搞笑','动物圈']
# 遍历top100视频，爬取分区数据
for ul in url_list:
    sec_response = requests.get(ul)
    sec_soup = BeautifulSoup(sec_response.text, 'html.parser')
    sec_items = sec_soup.findAll('ul', {'class': 'tag-area clearfix'})
    a = 0
    for si in sec_items:
        try: # 有的视频分区标签只有几个，用此跳过
            zoning1 = si.find_all('a',{'class': 'tag-link'})[a].text
            zoning2 = si.find_all('a', {'class': 'tag-link'})[a+1].text
            zoning3 = si.find_all('a', {'class': 'tag-link'})[a+2].text
            zoning4 = si.find_all('a', {'class': 'tag-link'})[a+3].text
            zoning5 = si.find_all('a', {'class': 'tag-link'})[a+4].text
            zoning6 = si.find_all('a', {'class': 'tag-link'})[a+5].text
            zoning7 = si.find_all('a', {'class': 'tag-link'})[a+6].text
            zoning8 = si.find_all('a', {'class': 'tag-link'})[a+7].text
            zoning9 = si.find_all('a', {'class': 'tag-link'})[a +8].text
            zoning10 = si.find_all('a', {'class': 'tag-link'})[a +9].text
        except IndexError :
            pass
        if zoning1 in all_zoning:
            zoning_list.append(zoning1)
        elif zoning2 in all_zoning:
            zoning_list.append(zoning2)
        elif zoning3 in all_zoning:
            zoning_list.append(zoning3)
        elif zoning4 in all_zoning:
            zoning_list.append(zoning4)
        elif zoning5 in all_zoning:
            zoning_list.append(zoning5)
        elif zoning6 in all_zoning:
            zoning_list.append(zoning6)
        elif zoning7 in all_zoning:
            zoning_list.append(zoning7)
        elif zoning8 in all_zoning:
            zoning_list.append(zoning8)
        elif zoning9 in all_zoning:
            zoning_list.append(zoning9)
        elif zoning10 in all_zoning:
            zoning_list.append(zoning10)
        print(len(zoning_list))

请原谅菜鸟拙劣得操作0-0