Python网络爬虫之提取&Beautiful Soup库入门学习笔记手札及代码实战
Beautiful Soup库入门学习
- 学习笔记手札及单元小结
- Beautiful Soup库的安装
- Beautiful Soup库的安装小测
- Beautiful Soup 库的基本元素
-
- Beautiful Soup库的引用
- BeautifulSoup类
- Tag标签
- Tag的name（名字）
- Tag的attrs(属性)
- Tag的NavigableString
- Tag的Comment
- 基于bs4库的HTML内容遍历方法
-
- 标签树的下行遍历
- 标签树的上行遍历
- 标签树的平行遍历
- 基于bs4库的HTML格式输出
-
- bs4库的prettify()方法
- bs4库的编码
学习笔记手札及单元小结
Beautiful Soup库的安装
https://www.crummy.com/software/BeautifulSoup/
Win平台：“以管理员身份运行”cmd
执行 pip install beautifulsoup4
Beautiful Soup库的安装小测
此处用Requests库获取demo.html源代码：
>>> import requests
>>> r = requests.get("http://python123.io/ws/demo.html")
>>> r.text
'This is a python demo page \r\n\r\nThe demo python introduces several python courses.
\r\nPython is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\r\nBasic Python and Advanced Python.
\r\n'
>>> demo = r.text
此处引入BeautifulSoup库
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo,'html.parser')
>>> print(soup.prettify())
<html>
<head>
<title>
This is a python demo page
</title>
</head>
<body>
<p class="title">
<b>
The demo python introduces several python courses.
</b>
</p>
<p class="course">
Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">
Basic Python
</a>
and
<a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">
Advanced Python
</a>
.
</p>
</body>
</html>
from bs4 import BeautifulSoup
soup = BeautifulSoup('data
','html.parser')
Beautiful Soup 库的基本元素
Beautiful Soup库是解析 遍历 维护 “标签树”的功能库
Beautiful Soup库的引用
from bs4 import BeautifulSoup
import bs4
BeautifulSoup类
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup("data","html.parser")
>>> soup2 = BeautifulSoup(open("D://demo.html"),"html.parser")
Tag标签
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo,"html.parser")
>>> soup.title
<title>This is a python demo page</title>
>>> tag = soup.a
>>> tag
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
Tag的name（名字）
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo,"html.parser")
>>> soup.a.name
'a'
>>> soup.a.parent.name
'p'
>>> soup.a.parent.parent.name
'body'
Tag的attrs(属性)
一个可以有0或多个属性，字典类型
>>> tag = soup.a
>>> tag.attrs
{
'href': 'http://www.icourse163.org/course/BIT-268001', 'class': ['py1'], 'id': 'link1'}
>>> tag.attrs['class']
['py1']
>>> tag.attrs['href']
'http://www.icourse163.org/course/BIT-268001'
>>> type(tag.attrs)
<class 'dict'>
>>> type(tag)
<class 'bs4.element.Tag'>
Tag的NavigableString
NavigableString可以跨越多个层次
>>> soup.a
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
>>> soup.a.string
'Basic Python'
>>> soup.p
<p class="title"><b>The demo python introduces several python courses.</b></p>
>>> soup.p.string
'The demo python introduces several python courses.'
>>> type(soup.p.string)
<class 'bs4.element.NavigableString'>
Tag的Comment
Comment是一种特殊类型
>>> newsoup = BeautifulSoup("This is not a coment
","html.parser")
>>> newsoup.b.string
'This is a comment'
>>> type(newsoup.b.string)
<class 'bs4.element.Comment'>
>>> newsoup.p.string
'This is not a coment'
>>> type(newsoup.p.string)
<class 'bs4.element.NavigableString'>
基于bs4库的HTML内容遍历方法
标签树的下行遍历
>>> soup = BeautifulSoup(demo,"html.parser")
>>> soup.head
<head><title>This is a python demo page</title></head>
>>> soup.head.contents
[<title>This is a python demo page</title>]
>>> soup.body.contents
['\n', <p class="title"><b>The demo python introduces several python courses.</b></p>, '\n', <p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a> and <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>.</p>, '\n']
>>> len(soup.body.contents)
5
>>> soup.body.contents[1]
<p class="title"><b>The demo python introduces several python courses.</b></p>
标签树的上行遍历
>>> soup = BeautifulSoup(demo,"html.parser")
>>> soup.title.parent
<head><title>This is a python demo page</title></head>
>>> soup.html.parent
<html><head><title>This is a python demo page</title></head>
<body>
<p class="title"><b>The demo python introduces several python courses.</b></p>
<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a> and <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>.</p>
</body></html>
>>> soup.parent
标签树的平行遍历
>>> soup = BeautifulSoup(demo,"html.parser")
>>> soup.a.next_sibling
' and '
>>> soup.a.next_sibling.next_sibling
<a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>
>>> soup.a.previous_sibling
'Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\r\n'
>>> soup.a.previous_sibling.previous_sibling
>>> soup.a.parent
<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a> and <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>.</p>
基于bs4库的HTML格式输出
bs4库的prettify()方法
>>> import requests
>>> r = requests.get("http://python123.io/ws/demo.html")
>>> demo = r.text
>>> demo
'This is a python demo page \r\n\r\nThe demo python introduces several python courses.
\r\nPython is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\r\nBasic Python and Advanced Python.
\r\n'
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo,"html.parser")
>>> soup.prettify()
'\n \n \n This is a python demo page\n \n \n \n \n \n The demo python introduces several python courses.\n \n
\n \n Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\n \n Basic Python\n \n and\n \n Advanced Python\n \n .\n
\n \n'
>>> print(soup.prettify())
<html>
<head>
<title>
This is a python demo page
</title>
</head>
<body>
<p class="title">
<b>
The demo python introduces several python courses.
</b>
</p>
<p class="course">
Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">
Basic Python
</a>
and
<a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">
Advanced Python
</a>
.
</p>
</body>
</html>
>>> print(soup.a.prettify())
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">
Basic Python
</a>
bs4库的编码
bs4库将任何HTML输入都变成utf-8编码
>>> soup = BeautifulSoup("中文
","html.parser")
>>> soup.p.string
'中文'
>>> print(soup.p.prettify())
<p>
中文
</p>