Python爬虫包BeautifulSoup异常处理(二)
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)
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