面对网络不稳定，页面更新等问题，很可能出现程序异常的问题，所以我们要对程序进行一些异常处理。大家可能觉得处理异常是一个比较麻烦的活，但在面对复杂网页和任务的时候，无疑成为一个很好的代码习惯。
网页‘404'、‘500'等问题
try:
html = urlopen('http://www.pmcaff.com/2221')
except HTTPError as e:
print(e)
返回的是空网页
if html is None:
print('没有找到网页')
目标标签在网页中缺失
try:
#不存在的标签
content = bsObj.nonExistingTag.anotherTag
except AttributeError as e:
print('没有找到你想要的标签')
else:
if content == None:
print('没有找到你想要的标签')
else:
print(content)
实例
if sys.version_info[0] == 2:
from urllib2 import urlopen # Python 2
from urllib2 import HTTPError
else:
from urllib.request import urlopen # Python3
from urllib.error import HTTPError
from bs4 import BeautifulSoup
import sys
def getTitle(url):
try:
html = urlopen(url)
except HTTPError as e:
print(e)
return None
try:
bsObj = BeautifulSoup(html.read())
title = bsObj.body.h1
except AttributeError as e:
return None
return title
title = getTitle("http://www.pythonscraping.com/exercises/exercise1.html")
if title == None:
print("Title could not be found")
else:
print(title)
以上全部为本篇文章的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。
