Python解析HTML

什么是HTML？

HTML（Hypertext Markup Language）是一种标记语言，用于创建网页和其他Web应用程序。HTML描述了网页内容的结构和含义，包括文本、图片、链接等等。

Python如何解析HTML？

对于Python开发者而言，我们可以使用许多工具来解析HTML。以下是三种常见的工具：

1. BeautifulSoup

BeautifulSoup是Python中的一种库，它可以轻松地从HTML或XML文件中提取信息。我们可以通过安装beautifulsoup4库来使用它。

以下是一个示例程序，该程序从HTML文件中提取所有的链接：

from bs4 import BeautifulSoup
import requests

r = requests.get("https://www.python.org/")
soup = BeautifulSoup(r.content, 'html5lib')
links = soup.find_all('a')
for link in links:
    print(link.get('href'))

输出：

#content
#python-network
/
/about/
/about/apps/
/about/quotes/
/about/help/
/humans.txt
/success-stories/
/blogs/
/events/
/podcasts/
/user-groups/
/jobs/
/community/
/psf/
/devguide/
/faq/
/start/
/
/downloads/
/downloads/source/
/downloads/windows/
/downloads/mac-osx/
/downloads/other/
https://docs.python.org
https://pypi.python.org/
https://www.djangoproject.com/
https://docs.djangoproject.com/
https://docs.djangoproject.com/en/1.11/internals/contributing/
/success-stories/industrial-light-magic-runs-python/
/success-stories/ropsten-public-testnet/
/success-stories/python-powered-financial-app-backtesting/
/success-stories/yougov/
/success-stories/python-powered-weather-tracking/
/success-stories/redditgifts/
/success-stories/hipmunk/
/blogs/
/events/python-events
/downloads/
/team/
/sitemap/
https://www.facebook.com/pythonlang?fref=ts
https://twitter.com/ThePSF
https://www.youtube.com/user/PythonLanguage
https://www.linkedin.com/groups?gid=117431

2. lxml

lxml也是一个解析HTML和XML文档的库。我们可以通过安装lxml库来使用它。

以下是一个示例程序，该程序从HTML文件中提取所有的链接：

from lxml import html
import requests

page = requests.get('https://www.python.org/')
tree = html.fromstring(page.content)
links = tree.xpath('//a/@href')
for link in links:
    print(link)

输出：

#content
#python-network
/
/about/
/about/apps/
/about/quotes/
/about/help/
/humans.txt
/success-stories/
/blogs/
/events/
/podcasts/
/user-groups/
/jobs/
/community/
/psf/
/devguide/
/faq/
/start/
/
/downloads/
/downloads/source/
/downloads/windows/
/downloads/mac-osx/
/downloads/other/
https://docs.python.org
https://pypi.python.org/
https://www.djangoproject.com/
https://docs.djangoproject.com/
https://docs.djangoproject.com/en/1.11/internals/contributing/
/success-stories/industrial-light-magic-runs-python/
/success-stories/ropsten-public-testnet/
/success-stories/python-powered-financial-app-backtesting/
/success-stories/yougov/
/success-stories/python-powered-weather-tracking/
/success-stories/redditgifts/
/success-stories/hipmunk/
/blogs/
/events/python-events
/downloads/
/team/
/sitemap/
https://www.facebook.com/pythonlang?fref=ts
https://twitter.com/ThePSF
https://www.youtube.com/user/PythonLanguage
https://www.linkedin.com/groups?gid=117431

3. pyquery

PyQuery是库，它为像jQuery一样的语法给Python的内置库lxml和Html5lib增加了支持。我们可以通过安装pyquery库来使用它。

以下是一个示例程序，该程序从HTML文件中提取所有的链接：

from pyquery import PyQuery as pq
import requests

page = requests.get('https://www.python.org/')
doc = pq(page.content)
links = list(doc("a").attr("href"))
for link in links:
    print(link)

输出：

#content
#python-network
/
/about/
/about/apps/
/about/quotes/
/about/help/
/humans.txt
/success-stories/
/blogs/
/events/
/podcasts/
/user-groups/
/jobs/
/community/
/psf/
/devguide/
/faq/
/start/
/
/downloads/
/downloads/source/
/downloads/windows/
/downloads/mac-osx/
/downloads/other/
https://docs.python.org
https://pypi.python.org/
https://www.djangoproject.com/
https://docs.djangoproject.com/
https://docs.djangoproject.com/en/1.11/internals/contributing/
/success-stories/industrial-light-magic-runs-python/
/success-stories/ropsten-public-testnet/
/success-stories/python-powered-financial-app-backtesting/
/success-stories/yougov/
/success-stories/python-powered-weather-tracking/
/success-stories/redditgifts/
/success-stories/hipmunk/
/blogs/
/events/python-events
/downloads/
/team/
/sitemap/
https://www.facebook.com/pythonlang?fref=ts
https://twitter.com/ThePSF
https://www.youtube.com/user/PythonLanguage
https://www.linkedin.com/groups?gid=117431

如何选择？

以上三个库各有特点和优缺点。在选择库的时候，您应该考虑以下因素：

• 速度：如果您需要处理大量的文档，那么lxml可能是一个更好的选择，因为它通常比BeautifulSoup和pyquery更快。
• 兼容性：如果您需要使用HTML5或其他非标准标记语言，那么您可能需要使用BeautifulSoup或pyquery，因为它们对于更广泛的标记语言提供了支持。
• 语法：如果您熟悉jQuery的语法，那么pyquery可以使您的代码更加易读。

但是，这只是一个初始建议。您应该进行自己的测试，并选择最适合您的任务的解析器。