Python爬虫之BeautifulSoup库

1. BeautifulSoup

1.1 解析库

1）Python标准库

# 使用方法BeautifulSoup(markup, \"html.parser\")# 优势Python的内置标准库，执行速度适中，文档容错能力强# 劣势Python2.7.3 或者 python3.2.2 前的版本容错能力差

2）lxml HTML解析器

绝大部分场景都应该使用lxml解析器

# 使用方法BeautifulSoup(markup, \"lxml\")# 优势速度快，文档容错能力强# 劣势需要安装C语言库

3）lxml XML解析器

# 使用方法BeautifulSoup(markup, \"xml\")# 优势速度快，唯一支持XML的解析器# 劣势需要安装C语言库

4）html5lib

# 使用方法BeautifulSoup(markup, \"html5lib\")# 优势最好的容错性，以浏览器的方式解析文档，生成HTML5格式的文档# 劣势速度慢，不依赖外部扩展

1.2 基本使用

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\') # 使用lxml解析器print(soup.prettify())    # 格式化代码，能自动将缺失的代码进行补全并进行容错处理print(soup.title.string)  # 拿到title标签，并拿到其中的内容

2. 标签选择器

2.1 选择元素

可以直接通过 .标签名 的方式来选择标签

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 th56cree 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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.title)        # 选择title标签，打印结果：<title>The Dormouse\'s story</title>print(type(soup.title))  # 类型：<class \'bs4.element.Tag\'>print(soup.head)print(soup.p) # 如果有多个匹配结果，那么它只会返回第一个

2.2 获取名称

获取标签的名称，如是p标签还是a标签等

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.title.name) # 获取标签名称

2.3 获取属性

可以通过 attrs[\”name\”] 或者 标签[\”name\”] 的方式来获取标签中name属性的值

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.p.attrs[\'name\'])   # 获取p标签中name属性的值print(soup.p[\'name\'])         # 这样也可以获取

2.4 获取内容

可以通过 标签.string 的方式来获取标签中的内容

html = \"\"\"<htad8ml><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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.p.string)  # 获取p标签中的内容（只是获取字符内容）：The Dormouse\'s story

2.5 嵌套选择

可以通过点 . 的方式来嵌套选择

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.head.title.string)  # 获取head下面的title中的字符内容

2.6 子节点和子孙节点

1）子节点

通过 标签.contents 可以获取标签中的所有子节点，保存为一个列表
保存为列表

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.p.contents)  # 获取p标签中的所有子节点，保存为一个列表

可以通过 标签.children 来获取标签中的所有子节点，保存为一个迭代器
保存为迭代器

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.p.children)  # 获取p标签中的所有子节点，保存为一个迭代器for i, child in enumerate(soup.p.children):print(i, child)

2）子孙节点

可以通过标签.descendants 来获取标签中的所有子孙节点，并保存为一个迭代器

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.p.descendants)   # 获取p标签中的所有子孙节点，保存为一个迭代器for i, child in enumerate(soup.p.descendants):print(i, child)

2.7 父节点和祖先节点

1）父节点

通过标签.parent 可以获取标签的父节点

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.a.parent)  # 获取a标签的父节点

2）祖先节点

通过标签.parents 可以获取标签的所有祖先节点

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(list(enumerate(soup.a.parents)))   # 获取a标签所有的祖先节点

2.8 兄弟节点

通过标签.next_siblings 可以获取标签后面的所有兄弟节点
通过标签.previous_siblings 可以获取标签前面的所有兄弟节点

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(list(enumerate(soup.a.next_siblings)))     # 获取a标签后面的所有兄弟节点print(list(enumerate(soup.a.previous_siblings))) # 获取a标签前面的所有兄弟节点

3. 标准选择器

3.1 find_all()

使用语法：find_all(name, attrs, recursive, text, **kwargs)

1）name

根据标签名来选择标签

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 BeautifulSoupsoup1 = BeautifulSoup(html, \'lxml\')print(soup1.find_all(\'ul\'))  # 找到所有匹配的结果，并以列表的形式返回print(type(soup1.find_all(\'ul\')[0]))soup2 = BeautifulSoup(html, \'lxml\')for ul in soup2.find_all(\'ul\'):print(ul.find_all(\'li\'))

2）attrs

根据标签中的属性进行选择标签

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.find_all(attrs={\'id\': \'list-1\'}))    # 找到所有的标签属性中id=list-1的标签print(soup.find_all(attrs={\'name\': \'elements\'}))soup2 = BeautifulSoup(html, \'lxml\')print(soup2.find_all(id=\'list-1\'))      # 找到所有的标签属性中id=list-1的标签，和attrs类似，只不过不需要再传入字典了print(soup2.find_all(class_=\'element\')) # 如果和关键字冲突，则可以通过将属性后面加一个下划线，如class_

3）text

根据文本的内容进行选择

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&lad8t;/li><li class=\"element\">Bar</li></ul></div></div>\'\'\'from bs4 import BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.find_all(text=\'Foo\'))   # 根据文本的内容进行选择，选择文本中包含Foo的标签的所有内容

3.2 find()

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.find(\'ul\'))   # 找到第一个ul标签print(type(soup.find(\'ul\')))print(soup.find(\'page\'))

3.3 find_parents() find_parent()

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

3.4 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。

3.5find_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。

3.6find_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。

3.7find_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。

4. CSS选择器

4.1 css选择器基本使用

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')print(soup.select(\'.panel .panel-heading\'))  # 这是类选择器，class=xxx，中间的空格表示这是也是层级选择器print(soup.select(\'ul li\'))                  # 这是标签选择器，选择具体的标签，这里表示选择ul标签中的li标签print(soup.select(\'#list-2 .element\'))       # 这个id选择器，id=xxxprint(type(soup.select(\'ul\')[0]))soup2 = BeautifulSoup(html, \'lxml\')for ul in soup2.select(\'ul\'):print(ul.select(\'li\'))

4.2 获取属性

TAG[\’id\’]
TAG.attr[\’id\’]

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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')for ul in soup.select(\'ul\'):print(ul[\'id\'])         # 获取ul标签中id属性的值print(ul.attrs[\'id\'])   # 这两种写法等价

4.3 获取内容

TAG.get_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 BeautifulSoupsoup = BeautifulSoup(html, \'lxml\')for li in soup.select(\'li\'):print(li.get_text())   # 获取标签中的文本

5. 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()
要记住常用的获取属性和文本值的方法