主要用途为获取网页元素。
1. 解析器类型
| 解析器 | 使用方法 | 优势 | 劣势 |
|---|---|---|---|
| Python标准库 | BeautifulSoup(markup, "html.parser") | Python的内置标准库、执行速度适中 、文档容错能力强 | Python 2.7.3 or 3.2.2)前的版本中文容错能力差 |
| lxml HTML 解析器 | BeautifulSoup(markup, "lxml") | 速度快、文档容错能力强 | 需要安装C语言库 |
| lxml XML 解析器 | BeautifulSoup(markup, "xml") | 速度快、唯一支持XML的解析器 | 需要安装C语言库 |
| html5lib | BeautifulSoup(markup, "html5lib") | 最好的容错性、以浏览器的方式解析文档、生成HTML5格式的文档 | 速度慢、不依赖外部扩展 |
2. 基本使用
1）使用prettify()来进行补全与处理获取网页元素的错误
html = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
<p class="story">Once upon a time there were three little sisters; and their names were
<a href="http://example.com/elsie" class="sister" id="link1"><!-- Elsie --></a>,
<a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.prettify()) #容错处理
print(soup.title.string)#获取title标签中的文字
2）选择器
a)得到BeautifulSoup对象
from bs4 import BeautifulSoup
soup = BeautifulSoup(html,'lxml')
b)选择标签
print(soup.title)
print(type(soup.title))
print(soup.head)
print(soup.p)
"""
<title>The Dormouse's story</title>
<class 'bs4.element.Tag'>
<head><title>The Dormouse's story</title></head>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
"""
c)选择标签元素
（获取的都是第一个匹配到的元素）
1. 获取名称
print(soup.title.name)
#title
2. 获取标签属性
print(soup.p.attrs['name'])
print(soup.p['name'])
"""
dromouse
dromouse
"""
3. 获取内容
print(soup.p.string)
#The Dormouse's story
3）获取子孙节点，父节点及兄弟节点
a) contents获取列表类型的节点内容（只将子节点作为一个list项输出出来）
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.p.contents)
"""
['\n Once upon a time there were three little sisters; and their names were\n ', <a class="sister" href="http://example.com/elsie" id="link1">
<span>Elsie</span>
</a>, '\n', <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>, ' \n and\n ', <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>, '\n and they lived at the bottom of a well.\n ']
"""
b)children获取list_iterator object类型(只输出到子节点）
from bs4 import BeautifulSoup
soup = BeautifulSoup(html,'lxml')
print(soup.p.children)
for i,child in enumerate(soup.p.children)
print(i,child)
"""
<list_iterator object at 0x7ff476c387f0>
0
Once upon a time there were three little sisters; and their names were
1 <a class="sister" href="http://example.com/elsie" id="link1">
<span>Elsie</span>
</a>
2
3 <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>
4
and
5 <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>
6
and they lived at the bottom of a well.
"""
c) descendants迭代获取所有的子孙节点
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.p.descendants)
for i, child in enumerate(soup.p.descendants):
print(i, child)
"""
<generator object descendants at 0x10650e678>
0
Once upon a time there were three little sisters; and their names were
1 <a class="sister" href="http://example.com/elsie" id="link1">
<span>Elsie</span>
</a>
2
3 <span>Elsie</span>
4 Elsie
5
6
7 <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>
8 Lacie
9
and
10 <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>
11 Tillie
12
"""
d)parent与parents获取父节点与子孙节点
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.a.parent)
"""
<p class="story">
Once upon a time there were three little sisters; and their names were
<a class="sister" href="http://example.com/elsie" id="link1">
<span>Elsie</span>
</a>
<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>
and
<a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>
and they lived at the bottom of a well.
</p>
"""
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(list(enumerate(soup.a.parents)))
"""
[(0, <p class="story">
Once upon a time there were three little sisters; and their names were
<a class="sister" href="http://example.com/elsie" id="link1">
<span>Elsie</span>
</a>
<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>
and
<a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>
and they lived at the bottom of a well.
</p>), (1, <body>
<p class="story">
Once upon a time there were three little sisters; and their names were
<a class="sister" href="http://example.com/elsie" id="link1">
<span>Elsie</span>
</a>
<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>
and
<a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>
and they lived at the bottom of a well.
</p>
<p class="story">...</p>
</body>), (2, <html>
<head>
<title>The Dormouse's story</title>
</head>
<body>
<p class="story">
Once upon a time there were three little sisters; and their names were
<a class="sister" href="http://example.com/elsie" id="link1">
<span>Elsie</span>
</a>
<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>
and
<a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>
and they lived at the bottom of a well.
</p>
<p class="story">...</p>
</body></html>), (3, <html>
<head>
<title>The Dormouse's story</title>
</head>
<body>
<p class="story">
Once upon a time there were three little sisters; and their names were
<a class="sister" href="http://example.com/elsie" id="link1">
<span>Elsie</span>
</a>
<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>
and
<a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>
and they lived at the bottom of a well.
</p>
<p class="story">...</p>
</body></html>)]
"""
e)next_siblings与previous_siblings获取兄弟节点
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(list(enumerate(soup.a.next_siblings)))
print(list(enumerate(soup.a.previous_siblings)))
4）标准选择器
find_all( name , attrs , recursive , text , **kwargs )
html='''
<div class="panel">
<div class="panel-heading">
<h4>Hello</h4>
</div>
<div class="panel-body">
<ul class="list" id="list-1">
<li class="element">Foo</li>
<li class="element">Bar</li>
<li class="element">Jay</li>
</ul>
<ul class="list list-small" id="list-2">
<li class="element">Foo</li>
<li class="element">Bar</li>
</ul>
</div>
</div>
'''
根据标签去取元素
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
for ul in soup.find_all('ul'):
print(ul.find_all('li'))
“”“
得到一个包含结果的列表类型
[<li class="element">Foo</li>, <li class="element">Bar</li>, <li class="element">Jay</li>]
[<li class="element">Foo</li>, <li class="element">Bar</li>]
”“”
使用名称来获取对象：
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.find_all(attrs={'id': 'list-1'}))
print(soup.find_all(attrs={'name': 'elements'}))
使用id或者class来获取指定元素列表对象：
from bs4 import BeautifulSoup
soup = BeautifulSoup(html,'lxml')
print(soup.find_all(id='list-1'))
print(soup.find_all(class_='element')) #class一定要加‘_'
"""
[<ul class="list" id="list-1" name="elements">
<li class="element">Foo</li>
<li class="element">Bar</li>
<li class="element">Jay</li>
</ul>]
[<li class="element">Foo</li>, <li class="element">Bar</li>, <li class="element">Jay</li>, <li class="element">Foo</li>, <li class="element">Bar</li>]
"""
做字符匹配：
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.find_all(text='Foo'))
#['Foo', 'Foo']
5) CSS选择器：
CSS风格的选择器
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
print(soup.select('.panel .panel-heading'))#选择class="panel"中的class="panel-heading"元素
print(soup.select('ul li'))#选择ul标签中的li标签
print(soup.select('#list-2 .element'))#选择id=“list-2”中的class="element"元素
print(type(soup.select('ul')[0]))
获取标签中的文本：
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, 'lxml')
for li in soup.select('li'):
print(li.get_text())
"""
Foo
Bar
Jay
Foo
Bar
"""
