问题遇到的现象和发生背景 爬取图片网站想获得href时报错

问题相关代码，请勿粘贴截图 i

import requests
from bs4 import BeautifulSoup
domain = "https://www.umei.cc/"
resp=requests.get(domain)
resp.encoding='utf-8'#处理乱码
#print(resp.text)

#把源代码交给bs4

main_page=BeautifulSoup(resp.text,"html.parser")
alist=main_page.find("div",class_="main-left left").find_all("a")
print(alist)

运行结果及报错内容

Traceback (most recent call last):
File "C:\Users\Administrator\PycharmProjects\pythonProject9\抓取图片.py", line 15, in
alist=list.find_all("a")
AttributeError: 'NoneType' object has no attribute 'find_all'

alist=main_page.find("div",class_="main-left left").find_all("a")
.find("div",class_="main-left left")的时候没有找到拥有class属性值位main-left left的div
它的值就是空，你在对空值进行find_all("a")就报错了