爬虫利器BeautifulSoup模块使用

Posted 2020-10-22 W-D

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一、简介

BeautifulSoup 是一个可以从html或XML文件中提取数据的Python库.它能够通过你喜欢的转换器实现惯用的文档导航,查找,修改文档的方式，同时应用场景也是非常丰富，你可以使用它进行XSS过滤，也可以是使用它来提取html中的关键信息。

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

二、安装

1.安装模块

easy_install beautifulsoup4
pip3 install beautifulsoup4

2.安装解析器（可以使用内置的解析器）

#Ubuntu
$ apt-get install Python-lxml
#centos/redhat
$ easy_install lxml
$ pip install lxml

3.各个解释器优缺点比较

三、开始使用，基本属性介绍

创建对象

将一段文档传入BeautifulSoup 的构造方法,就能得到一个文档的对象, 可以传入一段字符串或一个文件句柄。

from bs4 import BeautifulSoup

soup = BeautifulSoup(open("index.html"))

soup = BeautifulSoup("<html><body>...</body></html>")
###使用解释器###
soup = BeautifulSoup(open("index.html"), features="lxml")

基本使用

使用html示例

from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><b>wd</b></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""

soup=BeautifulSoup(html_doc,features="html.parser")
print(soup.head)#获取head标签
print(soup.head.title)#获取title
print(soup.body.a)

tips：通过soup.方式获取的标签如果标签有多个，只返回第一个标签

1.name：标签名称，如：<a>标签的名称为a，<span>标签名称为span

操作方式：获取、设置,设置以后会使得原文档标签改变

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd

from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><b>wd</b></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""
soup=BeautifulSoup(html_doc,features="html.parser")
print(soup.body.name)#获取标签名称
soup.body.p.name=\'span\'#设置标签名称
print(soup)

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2.attrs：标签属性(如id，class，style等)
操作方式：获取、设置

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><b>wd</b></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""
soup=BeautifulSoup(html_doc,features="html.parser")
print(soup.body.p.attrs)#获取标签所有属性
soup.body.p.attrs[\'id\']=\'user\'#设置／添加属性
print(soup.body.p.attrs.get(\'class\'))#获取标签具体的某个属性，当然可以通过soup.body.p.attrs[\'class\']获取
soup.body.p.attrs[\'class\']=["hide","a1"]#设置多个属性
print(soup)

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3.string:标签内容（类似js中的innertext），该属性只能适用于标签中只有一个内容，若有多个子标签都有内容则返回None

操作方式：获取、设置

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><b>wd</b></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""
soup=BeautifulSoup(html_doc,features="html.parser")
print(soup.head.title.string)#获取内容
soup.head.title.string=\'name\'#设置内容
print(soup)

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4.contents:将子节点以列表方式输出，返回list(),列表中仅仅含有子标签

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><a>wd</a></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""
soup=BeautifulSoup(html_doc,features="html.parser")
a=soup.body.contents
print(a)
print(type(a))

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5.childen:和contents不同，它返回列表生成器，使用循环获取，生成器中只含有子标签

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><a>wd</a></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""
soup=BeautifulSoup(html_doc,features="html.parser")
a=soup.body.children
print(type(a))
for item in a: 
    print(item)

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6.descendants:返回子子孙孙标签，返回迭代器

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><a>wd</a></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""
soup=BeautifulSoup(html_doc,features="html.parser")
a=soup.body.descendants
print(type(a))
for k,v in enumerate(a):
    print(k,v)

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7.strings&stripped_strings:返回所有子子孙孙标签内容生成器，stripped_strings和strings区别是，stripped_strings输出的是去掉空格的内容。

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><b>wd</b></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""

soup=BeautifulSoup(html_doc,features="html.parser")
for k,v in enumerate(soup.body.strings):
    print(k,v)
for k1,v1 in enumerate(soup.body.stripped_strings):
    print(k1,v1)
复制代码

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8.parent&parents:父标签（节点）和祖辈节点，父标签一般只有一个，祖辈节点可能很多，parents返回生成器。

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><a>wd</a></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""

soup=BeautifulSoup(html_doc,features="html.parser")
print(soup.a.parent)#a标签的父节点
b=list(enumerate(soup.a.parents))
print(b)
for k,v in enumerate(soup.a.parents): #a标签的祖辈节点
    print(k,v)

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9.next_sibling&previous_sibling：兄弟标签（节点），一般只有一个,没有返回none

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><a>wd</a></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""

soup=BeautifulSoup(html_doc,features="html.parser")
print(soup.p.next_sibling)
print(soup.p.previous_sibling)
for k,v in enumerate(soup.p.next_siblings):
    print(k,v)

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10.next_siblings&previous_siblings:返回所有兄弟标签的生成器。

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>test</title></head>
    <body>
<p class="title"><a>wd</a></p>
<p class="story">
<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>
</p>
<p class="story">...</p>
</body>
</html>
"""

soup=BeautifulSoup(html_doc,features="html.parser")
for k,v in enumerate(soup.p.next_siblings):
    print(k,v)
for k1,v1 in enumerate(soup.p.previous_siblings):
    print(k1,v1)

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11.hidden:隐藏或显示当前标签，只会把当前标签隐藏，子孙标签不变

soup=BeautifulSoup(html_doc,features="html.parser")
tag = soup.find(\'body\')
tag.hidden=True#设置body标签隐藏
print(tag)
print(soup)

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12.is_empty_element,是否是空标签(是否可以是空)或者自闭合标签

# tag = soup.find(\'br\')
# v = tag.is_empty_element
# print(v)

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四、强大的过滤器

这里所说的过滤器可以理解为查找文档的参数，可以是字符串，可以是name，可以是正则表达式等等，过滤器依赖于过滤方法，下面介绍常用过滤方法。

1.find_all(self, name=None, attrs={}, recursive=True, text=None, limit=None, **kwargs): 获取匹配的所有标签（节点），返回列表

name：标签名，字符串对象会被忽略，可以是字符串、正则、列表、方法或者True
attrs：标签属性，字典形式，用于查找标签的特殊属性
recursive:是否递归查找，设置Flase，只查找子节点.
text:文档中的字符串内容，与name参数一样，可接受字符串、正则、列表、或者True
limit：限制列表中个数，如limit=3只返回前三个

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>The Dormouse\'s story</title></head>
<body>
asdf
    <div class="title">
        <b>The Dormouse\'s story总共</b>
        <h1>f</h1>
    </div>
<div class="story">Once upon a time there were three little sisters; and their names were
    <a  class="sister0" id="link1">Els<span>f</span>ie</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.</div>
ad<br/>sf
<p class="story">...</p>
</body>
</html>
"""
soup=BeautifulSoup(html_doc,features="html.parser")
# tags = soup.find_all(\'a\')
# print(tags)

# tags = soup.find_all(\'a\',limit=1)
# print(tags)

# tags = soup.find_all(name=\'a\', attrs={\'class\': \'sister\'}, recursive=True, text=\'Lacie\')
# # tags = soup.find(name=\'a\', class_=\'sister\', recursive=True, text=\'Lacie\')
# print(tags)


# ####### 列表 #######
# v = soup.find_all(name=[\'a\',\'div\'])
# print(v)

# v = soup.find_all(class_=[\'sister0\', \'sister\'])
# print(v)

# v = soup.find_all(text=[\'Tillie\'])
# print(v, type(v[0]))


# v = soup.find_all(id=[\'link1\',\'link2\'])
# print(v)

# v = soup.find_all(href=[\'link1\',\'link2\'])
# print(v)

# ####### 正则 #######
import re
# rep = re.compile(\'p\')
# rep = re.compile(\'^p\')
# v = soup.find_all(name=rep)
# print(v)

# rep = re.compile(\'sister.*\')
# v = soup.find_all(class_=rep)
# print(v)

# rep = re.compile(\'http://www.oldboy.com/static/.*\')
# v = soup.find_all(href=rep)
# print(v)

# ####### 方法筛选 #######
# def func(tag):
# return tag.has_attr(\'class\') and tag.has_attr(\'id\')
# v = soup.find_all(name=func)
# print(v)


# ## get,获取标签属性
# tag = soup.find(\'a\')
# v = tag.get(\'id\')
# print(v)

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2.find_all(self, name=None, attrs={}, recursive=True, text=None, limit=None, **kwargs): 获取匹配的一个（节点），返回tag对象，用法与find_all相同

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from bs4 import BeautifulSoup
html_doc = """
<html><head><title>The Dormouse\'s story</title></head>
<body>
asdf
    <div class="title">
        <b>The Dormouse\'s story总共</b>
        <h1>f</h1>
    </div>
<div class="story">Once upon a time there were three little sisters; and their names were
    <a  class="sister0" id="link1">Els<span>f</span>ie</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.</div>
ad<br/>sf
<p class="story">...</p>
</body>
</html>
"""
soup=BeautifulSoup(html_doc,features="html.parser")
tag = soup.find(\'a\')
print(tag.name)

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3.其他过滤方法：

tag.find_next(...)                   #返回后面第一个符合条件的节点
tag.find_all_next(...)              #返回后面所有符合条件的节点
tag.find_next_sibling(...)        #返回后面第一个兄弟节点
tag.find_next_siblings(...)      #返回后面所有兄弟节点
 
tag.find_previous(...)             #返回前面一个符合条件的节点
tag.find_all_previous(...)        #返回前面所有符合条件的节点
tag.find_previous_sibling(...)  #返回前面第一个兄弟节点
tag.find_previous_siblings(...) #返回前面所有兄弟节点
 
tag.find_parent(...)    #返回所有祖先节点
tag.find_parents(...)   #返回直接父节点
 
# 参数同find_all

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五、CSS选择器

BeautifulSoup不仅提供了筛选器，也提供了选择器，用法和前端css一样，其中.代表class，#代表id

html_doc = """
<html><head><title>The Dormouse\'s story</title></head>
<body>
asdf
    <div class="title">
        <b>The Dormouse\'s story总共</b>
        <h1>f</h1>
    </div>
<div class="story">Once upon a time there were three little sisters; and their names were
    <a  class="sister0" id="link1">Els<span>f</span>ie</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.</div>
ad<br/>sf
<p class="story">...</p>
</body>
</html>
"""
 
soup = BeautifulSoup(html_doc, features="lxml")
soup.select("title")

soup.select("p nth-of-type(3)")
 
soup.select("body a")
 
soup.select("html head title")
 
tag = soup.select("span,a")
 
soup.select("head > title")
 
soup.select("p > a")
 
soup.select("p > a:nth-of-type(2)")
 
soup.select("p > #link1")
 
soup.select("body > a")
 
soup.select("#link1 ~ .sister")
 
soup.select("#link1 + .sister")
 
soup.select(".sister")
 
soup.select("[class~=sister]")
 
soup.select("#link1")
 
soup.select("a#link2")
 
soup.select(\'a[href]\')
 
soup.select(\'a[href="http://example.com/elsie"]\')
 
soup.select(\'a[href^="http://example.com/"]\')
 
soup.select(\'a[href$="tillie"]\')
 
soup.select(\'a[href*=".com/el"]\')
 
 
from bs4.element import Tag
 
def default_candidate_generator(tag):
    for child in tag.descendants:
        if not isinstance(child, Tag):
            continue
        if not child.has_attr(\'href\'):
            continue
        yield child
 
tags = soup.find(\'body\').select("a", _candidate_generator=default_candidate_generator)
print(type(tags), tags)
 
from bs4.element import Tag
def default_candidate_generator(tag):
    for child in tag.descendants:
        if not isinstance(child, Tag):
            continue
        if not child.has_attr(\'href\'):
            continue
        yield child
 
tags = soup.find(\'body\').select("a", _candidate_generator=default_candidate_generator, limit=1)
print(type(tags), tags)

六、tag对象常用方法

1.clear():将标签的所有子标签全部清空（保留标签名）

# tag = soup.find(\'body\')
# tag.clear()
# print(soup)

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2.decompose():递归的删除所有的标签

soup=BeautifulSoup(html_doc,features="html.parser")
body = soup.find(\'body\')
body.decompose()#body自身标签也会删除
print(soup)

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3.extract():递归的删除所有的标签，并获取删除的标签

soup=BeautifulSoup(html_doc,features="html.parser")
body = soup.find(\'body\')
a=body.extract()
print(a)
print(soup)

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4.decode()&decode_contents():decode,转换为字符串（含当前标签）,decode_contents（不含当前标签）

soup=BeautifulSoup(html_doc,features="html.parser")
body = soup.find(\'body\')
a=body.decode()
b=body.decode_contents()
print(type(a))
print(type(b))

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5.encode()&encode_contents():encode,转换为bytes类型（含当前标签）,encode_contents（不含当前标签）

soup=BeautifulSoup(html_doc,features="html.parser")
body = soup.find(\'body\')
a=body.encode()
b=body.encode_contents()
print(type(a))
print(type(b))

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6. has_attr():检查标签是否具有该属性,返回布尔类型

soup=BeautifulSoup(html_doc,features="html.parser")
tag = soup.find(\'a\')
print(tag.has_attr(\'id\'))

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7. get_text():获取标签内部文本内容

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