Beautiful Soup库基础用法（爬虫）

简介

官方文档：https://www.crummy.com/software/BeautifulSoup/bs4/doc/#

中文文档：https://www.crummy.com/software/BeautifulSoup/bs4/doc/index.zh.html

Beautiful Soup 是一个可以从HTML或XML文本中提取数据的Python库，它能对HTML、XML格式进行解析成树形结构并提取相关信息。

Beautiful Soup库是一个灵活又方便的网页解析库，处理高效，支持多种解析库（后面会介绍），利用它不用编写正则表达式即可方便地实现网页信息的提取。

安装

Beautiful Soup 3 目前已经停止开发，推荐在现在的项目中使用Beautiful Soup 4，安装方法：

pip install beautifulsoup4

Beautiful Soup库的4种解析器

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

如果仅是想要解析HTML文档，只要用文档创建 BeautifulSoup 对象就可以了。Beautiful Soup会自动选择一个解析器来解析文档.但是还可以通过参数指定使用那种解析器来解析当前文档。BeautifulSoup 第一个参数应该是要被解析的文档字符串或是文件句柄,第二个参数用来标识怎样解析文档.如果第二个参数为空,那么Beautiful Soup根据当前系统安装的库自动选择解析器,解析器的优先数序: lxml, html5lib, Python标准库(python自带的解析库).

安装解析器库：

pip install html5lib

pip  install lxml

Beautiful Soup类的基本元素

基本使用

容错处理,文档的容错能力指的是在html代码不完整的情况下,使用该模块可以识别该错误。使用BeautifulSoup解析上述代码,能够得到一个 BeautifulSoup 的对象,并能按照标准的缩进格式的结构输出

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())  #处理好缩进，结构化显示

print(soup.title.string)

<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 class="sister" href="http://example.com/elsie" id="link1">

    <!-- Elsie -->

   </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>

The Dormouse's story

output

标签选择器

选择标签元素（存在多个取第一个）

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.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>

output

获取名称

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.title.name)

title

获取属性

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.p.attrs['name'])

print(soup.p['name'])  # 也可以这样写

dromouse

dromouse

获取内容

html = """

<html><head><title>The Dormouse's story</title></head>

<body>

<p clss="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.p.string)

The Dormouse's story

这里有一个坑：

解决方法就是做判断(需要导入import bs4)：

if type(soup.b.string)==bs4.element.Comment:

    pass

还有一点需要注意：NavigableString可以跨越多个层次

嵌套选择

html = """

<html><head><title>The Dormouse's story</title></head>

<body>

<div class="title" name="dromouse"><b class='bb'>The Dormouse's story</b></div>

<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.div.b['class'])

['bb']

多层嵌套时

html = """<html>

<head>

    <title>Fucking Title</title>

</head>

<body>

    <p class="title"><b><!--This is a fucking comment!-->chantress pheny carbamic picamar.</b></p>

    <p class="course">Lorem ipsum dolor sit amet laborum. <a href="http://www.baidu.com" class="py1" id="link1">Basic Python

        </a> and <a href="http://www.google.com" class="py2" id="link2">Python</a>.

    </p>

</body>

</html>"""

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

print(list(soup.p.stripped_strings))

['chantress pheny carbamic picamar.']

节点操作

子节点和子孙节点

对于一个标签的儿子节点不仅包括标签节点，也包括字符串节点，空格表示为'\n'

html = """

<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 href="http://example.com/elsie" class="sister" id="link1">

                <span>Elsie</span>

            </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.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        ']

output

html = """

<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 href="http://example.com/elsie" class="sister" id="link1">

                <span>Elsie</span>

            </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.p.children)

for i, child in enumerate(soup.p.children):

    print(i, child)

<list_iterator object at 0x1064f7dd8>

            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.

output

html = """

<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 href="http://example.com/elsie" class="sister" id="link1">

                <span>Elsie</span>

            </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.p.descendants)

for i, child in enumerate(soup.p.descendants):

    print(i, child)

<generator object descendants at 0x10650e678>

            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>

 <span>Elsie</span>

 Elsie

 <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>

 Lacie

            and

 <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>

 Tillie

            and they lived at the bottom of a well.

output

父节点和祖先节点

html = """

<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 href="http://example.com/elsie" class="sister" id="link1">

                <span>Elsie</span>

            </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.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>

output

html = """

<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 href="http://example.com/elsie" class="sister" id="link1">

                <span>Elsie</span>

            </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(list(enumerate(soup.a.parents)))

[(, <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>), (, <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>

<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>), (, <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>)]

output

兄弟节点

html = """

<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 href="http://example.com/elsie" class="sister" id="link1">

                <span>Elsie</span>

            </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(list(enumerate(soup.a.next_siblings)))

print(list(enumerate(soup.a.previous_siblings)))

[(, '\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        ')]

[(, '\n            Once upon a time there were three little sisters; and their names were\n            ')]

output

标准选择器

基于bs4库的HTML内容查找方法

<>.find_all(name,attrs,recursive,text,**kwargs)  # 返回一个列表类型,存储查找的结果

name      对标签名称的检索字符串

attrs     对标签属性值的检索字符串,可标注属性检索

recursive 是否对子孙全部搜索,默认True

text      对文本内容进行检索

由find_all()扩展的七个方法:

find_all( name , attrs , recursive , text , **kwargs )

可根据标签名、属性、内容查找文档

name

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>

'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

print(soup.find_all('ul'))

print(type(soup.find_all('ul')[0]))

[<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>]

<class 'bs4.element.Tag'>

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>

'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

for ul in soup.find_all('ul'):

    print(ul.find_all('li'))

[<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>]

output

attrs

html='''

<div class="panel">

    <div class="panel-heading">

        <h4>Hello</h4>

    </div>

    <div class="panel-body">

        <ul class="list" id="list-1" name="elements">

            <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>

'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

print(soup.find_all(attrs={'id': 'list-1'}))

print(soup.find_all(attrs={'name': 'elements'}))

[<ul class="list" id="list-1" name="elements">

<li class="element">Foo</li>

<li class="element">Bar</li>

<li class="element">Jay</li>

</ul>]

[<ul class="list" id="list-1" name="elements">

<li class="element">Foo</li>

<li class="element">Bar</li>

<li class="element">Jay</li>

</ul>]

output

也可以这样

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>

'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

print(soup.find_all(id='list-1'))

print(soup.find_all(class_='element'))

[<ul class="list" id="list-1">

<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>]

output

text

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>

'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

print(soup.find_all(text='Foo'))

['Foo', 'Foo']

find( name , attrs , recursive , text , **kwargs )

find返回单个元素，find_all返回所有元素

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>

'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

print(soup.find('ul'))

print(type(soup.find('ul')))

print(soup.find('page'))

<ul class="list" id="list-1">

<li class="element">Foo</li>

<li class="element">Bar</li>

<li class="element">Jay</li>

</ul>

<class 'bs4.element.Tag'>

None

find_parents() find_parent()

find_parents()返回所有祖先节点，find_parent()返回直接父节点。

find_next_siblings() find_next_sibling()

find_next_siblings()返回后面所有兄弟节点，find_next_sibling()返回后面第一个兄弟节点。

find_previous_siblings() find_previous_sibling()

find_previous_siblings()返回前面所有兄弟节点，find_previous_sibling()返回前面第一个兄弟节点。

find_all_next() find_next()

find_all_next()返回节点后所有符合条件的节点, find_next()返回第一个符合条件的节点

find_all_previous() 和 find_previous()

find_all_previous()返回节点后所有符合条件的节点, find_previous()返回第一个符合条件的节点

CSS选择器

通过select()直接传入CSS选择器即可完成选择

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>

'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

print(soup.select('.panel .panel-heading'))

print(soup.select('ul li'))

print(soup.select('#list-2 .element'))

print(type(soup.select('ul')[0]))

[<div class="panel-heading">

<h4>Hello</h4>

</div>]

[<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>]

[<li class="element">Foo</li>, <li class="element">Bar</li>]

<class 'bs4.element.Tag'>

output

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>

'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

for ul in soup.select('ul'):

    print(ul.select('li'))

[<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>]

output

获取属性

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>

'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

for ul in soup.select('ul'):

    print(ul['id'])

    print(ul.attrs['id'])

list-

list-

list-

list-

获取内容

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>

'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(html, 'lxml')

for li in soup.select('li'):

    print(li.get_text())

Foo

Bar

Jay

Foo

Bar

总结

推荐使用lxml解析库，必要时使用html.parser
标签选择筛选功能弱但是速度快
建议使用find()、find_all() 查询匹配单个结果或者多个结果
如果对CSS选择器熟悉建议使用select()

实例：中国大学排名爬虫

步骤1:从网络上获取大学排名网页内容getHTMLText()
步骤2:提取网页内容中信息到合适的数据结构fillUnivList()
步骤3:利用数据结构展示并输出结果printUnivLise()

import requests

from bs4 import BeautifulSoup

import bs4

def getHTMLText(url):

    try:

        r = requests.get(url, timeout=30)

        r.raise_for_status()

        r.encoding = r.apparent_encoding

        return r.text

    except:

        return "error"

def fillUnivList(ulist, html):

    soup = BeautifulSoup(html, "html.parser")

    for tr in soup.find('tbody').children:

        if isinstance(tr, bs4.element.Tag):  # 过滤掉非标签类型

            tds = tr('td')

            ulist.append([tds[0].string, tds[1].string, tds[3].string])

# 中文对齐问题的解决：

# 采用中文字符的空格填充 chr(12288)

def printUnivList(ulist, num):

    tplt = "{0:^10}\t{1:{3}^10}\t{2:^10}"

    print(tplt.format("排名", "学校名称", "总分", chr(12288)))

    for i in range(num):

        u = ulist[i]

        print(tplt.format(u[0], u[1], u[2], chr(12288)))

def main():

    uinfo = []

    url = 'http://www.zuihaodaxue.cn/zuihaodaxuepaiming2016.html'

    html = getHTMLText(url)

    fillUnivList(uinfo, html)

    printUnivList(uinfo, 20)

if __name__ == '__main__':

    main()