Python中第二个异常未生效？新手技术问题咨询

我是Python新手，编写了如下爬虫代码，设置了TypeError和AttributeError两个异常捕获分支，预期触发异常后最终返回"None"。但实际运行时第二个异常未执行，报错显示在处理TypeError时又触发AttributeError，疑惑是否因循环或缩进导致该问题？

爬虫代码 #

import requests
from bs4 import BeautifulSoup

headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.0.0 Safari/537.36'
}

for x in range(60,61):
    url = 'https://example.com/page/'
    r = requests.get(url+str(x), headers = headers)
    soup = BeautifulSoup(r.content, features='lxml')

    articles = soup.find_all('article', class_='blog-view')
    
    for item in articles:
        title = item.find('h2', class_="entry-title").text
        
        if title == "Premium" or title == "Deleted" or title == "deleted":
            image_url = "None"
        else:
            try:
                image_url = item.find('div', class_='entry-content').p.img['src']
            except TypeError:
                image_url = item.find('div', class_='wp-caption').img['src']
            except AttributeError:
                image_url = "None"
            print(image_url)

报错输出 #

TypeError
Cell In [10], line 30
     29 try:
---> 30     image_url = item.find('div', class_='entry-content').p.img['src']
     31 except TypeError:

TypeError: 'NoneType' object is not subscriptable

During handling of the above exception, another exception occurred:

AttributeError
Cell In [10], line 32
     30     image_url = item.find('div', class_='entry-content').p.img['src']
     31 except TypeError:
---> 32     image_url = item.find('div', class_='wp-caption').img['src']
     33 except AttributeError:
     34     image_url = "None"

AttributeError: 'NoneType' object has no attribute 'img'

不是循环或缩进的问题，核心原因是：except TypeError分支内的代码抛出了新的AttributeError，这个异常不在当前try-except块的处理范围内。

当第一个try块触发TypeError后，程序进入except TypeError分支执行代码，但这段代码里item.find('div', class_='wp-caption')返回了None，接着访问.img就会抛出AttributeError，而当前try-except的except AttributeError只负责处理try块内的异常，不会处理其他except分支里的异常，所以程序直接报错退出。

方法一：给except TypeError分支添加嵌套try-except #

把第二个查找逻辑也放进异常保护里：

try:
    image_url = item.find('div', class_='entry-content').p.img['src']
except TypeError:
    try:
        image_url = item.find('div', class_='wp-caption').img['src']
    except AttributeError:
        image_url = "None"
except AttributeError:
    image_url = "None"

方法二：拆分链式调用，提前判断节点是否存在 #

避免直接链式调用find().p.img['src']，先逐个判断节点是否存在，从根源上减少异常：

entry_content = item.find('div', class_='entry-content')
if entry_content and entry_content.p and entry_content.p.img:
    image_url = entry_content.p.img['src']
else:
    wp_caption = item.find('div', class_='wp-caption')
    if wp_caption and wp_caption.img:
        image_url = wp_caption.img['src']
    else:
        image_url = "None"

方法三：合并异常捕获，简化逻辑 #

直接捕获所有可能的异常，同时调整查找逻辑的顺序：

try:
    # 先尝试第一个选择器路径
    img_tag = item.find('div', class_='entry-content').p.find('img')
    if img_tag:
        image_url = img_tag['src']
    else:
        # 第一个路径找不到img，尝试第二个选择器
        img_tag = item.find('div', class_='wp-caption').find('img')
        image_url = img_tag['src']
except (TypeError, AttributeError):
    image_url = "None"

内容的提问来源于stack exchange，提问作者Vardhan