02：BeautifulSoup

1.1 BeautifulSoup介绍

　　1、BeautifulSoup作用

　　　　　　1、BeautifulSoup是一个模块，该模块用于接收一个HTML或XML字符串，然后将其进行格式化

　　　　　　2、之后遍可以使用他提供的方法进行快速查找指定元素，从而使得在HTML或XML中查找指定元素变得简单

　　2、安装

　　　　　　pip3 install beautifulsoup4

　　　　　　pip install lxml #lxml是一个比beautifulsoup4更强大的库（居然直接用pip就安装成功了）

　　3、lxml与html.parser比较

　　　　　　1. 两者都是把文本转成对象的方法，lxml是第三方库，但是性能好（生产用这个），html.parser 是python内置模块无需安装

　　　　　　2. soup = BeautifulSoup(response.text,features='lxml') #lxml是第三方库，但是性能好（生产用这个）

　　　　　　3. soup = BeautifulSoup(response.text,features='html.parser') # html.parser 是python内置模块无需安装

　　4、lxml结合BeautifulSoup举例

from bs4 import BeautifulSoup

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a</a>
    <a class="c1" id="link2" name="ha">i am a</a>
</body>
</html>
"""
soup = BeautifulSoup(html_doc, features="lxml")
#1、找到第一个a标签
tag1 = soup.find(name='a')
#2、找到所有的a标签
tag2 = soup.find_all(name='a')
#3、找到id＝link2的标签
tag3 = soup.select('#link2')

print(tag1)    # <a class="c1" id="i1" name="ha">i am a</a>
print(tag2)    # [<a class="c1" id="i1" name="ha">i am a</a>, <a class="c1" id="link2" name="ha">i am a</a>]
print(tag3)    # [<a class="c1" id="link2" name="ha">i am a</a>]

lxml结合BeautifulSoup举例

1.2 BeautifulSoup常用方法

　　1、name，标签名称（tag.name）

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a</a>
    <a class="c1" id="link2" name="ha">i am a</a>
</body>
</html>
"""

from bs4 import BeautifulSoup

soup = BeautifulSoup(html_doc, features="lxml")
tag = soup.find('a')    # 找到第一个a标签
print(tag.name)        # 获取标签名称（如果是a标签，name=a）
tag.name = 'span'      # 将获取的a标签变成span标签

print(soup)

# <html><head><title>The Dormouse's story</title></head>
# <body>
# <span class="c1" id="i1" name="ha">i am a</span>
# <a class="c1" id="link2" name="ha">i am a</a>
# </body>
# </html>

name，标签名称

　　2、attr，标签属性（tag.attrs）

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a</a>
    <a class="c1" id="link2" name="ha">i am a</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

tag = soup.find('a')
attrs = tag.attrs               # 获取所有属性
print(attrs)                    # 格式：{'name': 'ha', 'class': ['c1'], 'id': 'i1'}
tag.attrs = {'ik':123}          # 将属性替换成          ik="123"
tag.attrs['id'] = 'iiiii'      # 在原来的基础上添加一个 id="iiiii"属性
print(soup)                     # <a id="iiiii" ik="123">

attr，标签属性

　　3、children,所有子标签

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a</a>
    <a class="c1" id="link2" name="ha">i am a</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

body = soup.find('body')
v = body.children        #找到所有孩子标签

for tag in v:
    print(tag)
# <a class="c1" id="i1" name="ha">i am a</a>
# <a class="c1" id="link2" name="ha">i am a</a>

children,所有子标签

　　4、descendants,所有子子孙孙标签

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

body = soup.find('body')
v = body.descendants        #找到所有子子孙孙标签

for tag in v:
    print(tag)
# <a class="c1" id="i1" name="ha">i am a1</a>
# i am a1
# <a class="c1" id="link2" name="ha">i am a2</a>
# i am a2

descendants,所有子子孙孙标签

　　5、clear,将标签的所有子标签全部清空（保留标签名）

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

tag = soup.find('body')
tag.clear()              # 结果仅保留了body这个标签名，其他全部删除了

print(soup)
# <html><head><title>The Dormouse's story</title></head>
# <body></body>
# </html>

clear,将标签的所有子标签全部清空（保留标签名）

　　6、decompose,递归的删除所有的标签

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

body = soup.find('body')
body.decompose()        # 结果将body标签都删除了，不保留body这个标签名

print(soup)
# <html><head><title>The Dormouse's story</title></head>
# </html>

decompose,递归的删除所有的标签

　　7、extract,递归的删除所有的标签，并获取删除的标签

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

body = soup.find('body')
v = body.extract()

print(v)            # v就是删除的body标签的内容
# <body>
# <a class="c1" id="i1" name="ha">i am a1</a>
# <a class="c1" id="link2" name="ha">i am a2</a>
# </body>

print(soup)        # soup是将body标签删除后的内容，还保留body这个空标签
# <html><head><title>The Dormouse's story</title></head>
# </html>

extract,递归的删除所有的标签，并获取删除的标签

　　8、find,获取匹配的第一个标签

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

tag = soup.find('a')
print(tag)                # <a class="c1" id="i1" name="ha">i am a1</a>

# recursive=False那么只会到儿子里去查找，不会到子子孙孙查找
# text='Lacie'  文本必须是这样的
tag1 = soup.find(name='a', attrs={'class': 'sister'}, recursive=True, text='Lacie')
tag2 = soup.find(name='a', class_='sister', recursive=True, text='Lacie')
print(tag1)              # None
print(tag2)              # None

find,获取匹配的第一个标签

　　9、find_all,获取匹配的所有标签

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

#1、找到所有a标签
tags = soup.find_all('a')
print(tags)          # [<a class="c1" id="i1" name="ha">i am a1</a>, <a class="c1" id="link2" name="ha">i am a2</a>]

#2、limit=1限制只找一个
tags = soup.find_all('a',limit=1)      # limit限制只找多少个
print(tags)                           # [<a class="c1" id="i1" name="ha">i am a1</a>]

#3、找到所有的a标签和div标签
v = soup.find_all(name=['a','div'])
print(v)        # [<a class="c1" id="i1" name="ha">i am a1</a>, <a class="c1" id="link2" name="ha">i am a2</a>]

#4、找到所欲class名为：'sister0', 'sister'
v = soup.find_all(class_=['sister0', 'sister'])
print(v)          # []

#5、找到所有id='link1'或id='link2'的标签
# v = soup.find_all(href=['link1','link2'])  # 同理
v = soup.find_all(id=['link1','link2'])
print(v)           # [<a class="c1" id="link2" name="ha">i am a2</a>]


# ####### 正则 #######
import re
rep = re.compile('p')
rep = re.compile('^p')    #找到所有以p开头的标签
v = soup.find_all(name=rep)

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)

find_all,获取匹配的所有标签

　　10、decode,转换为字符串（含当前标签）；decode_contents（不含当前标签）

　　　　　　作用：将body这个对象转换成字符串类型

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

body = soup.find('body')

#1、包含body这个标签
v1 = body.decode()              #v1包含body这个标签
print(v1)
# <body>
# <a class="c1" id="i1" name="ha">i am a1</a>
# <a class="c1" id="link2" name="ha">i am a2</a>
# </body>

#2、不包含body这个标签
v2 = body.decode_contents()     #v2不包含body这个标签
print(v2)
# <a class="c1" id="i1" name="ha">i am a1</a>
# <a class="c1" id="link2" name="ha">i am a2</a>

decode,转换为字符串（含当前标签）；decode_contents（不含当前标签）

　　11、encode,转换为字节（含当前标签）；encode_contents（不含当前标签）

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

body = soup.find('body')

#1、包含body这个标签
v1 = body.encode()        #v1包含body这个标签（字节格式）
print(v1)
# b'<body>
<a class="c1" id="i1" name="ha">i am a1</a>
<a class="c1" id="link2" name="ha">i am a2</a>
</body>'

#2、不包含body这个标签
v2 = body.encode_contents()      #v2不包含body这个标签（字节格式）
print(v2)
# b'
<a class="c1" id="i1" name="ha">i am a1</a>
<a class="c1" id="link2" name="ha">i am a2</a>
'

encode,转换为字节（含当前标签）；encode_contents（不含当前标签）

　　12、has_attr,检查标签是否具有该属性

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

tag = soup.find('a')
v = tag.has_attr('id')
print(v)                # True

has_attr,检查标签是否具有该属性

　　13、get_text,获取标签内部文本内容

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

tag = soup.find('a')
v = tag.get_text('id')
print(v)                   # i am a1

get_text,获取标签内部文本内容

　　14、index,检查标签在某标签中的索引位置

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

tag = soup.find('body')
v = tag.index(tag.find('a'))
print(v)         # 1

index,检查标签在某标签中的索引位置

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

　　　　　　作用：判断是否是如下标签：'br' , 'hr', 'input', 'img', 'meta','spacer', 'link', 'frame', 'base'

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

tag = soup.find('a')
print(tag)                # <a class="c1" id="i1" name="ha">i am a1</a
v = tag.is_empty_element
print(v)                  # False

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

　　16、append在当前标签内部追加一个标签

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

tag = soup.find('body')

#1、找到指定第一个a标签追加到最后
tag.append(soup.find('a'))
print(soup)
# <html><head><title>The Dormouse's story</title></head>
# <body>
# <a class="c1" id="link2" name="ha">i am a2</a>
# <a class="c1" id="i1" name="ha">i am a1</a></body>
# </html>

#2、创建一个a标签追加到末尾
from bs4.element import Tag
obj = Tag(name='i',attrs={'id': 'it'})    #创建一个i标签，并设置属性
obj.string = '我是一个新来的'        #给他这个创建的i标签添加内容
tag = soup.find('body')
tag.append(obj)                #将创建的a标签添加到body中

print(soup)
# <html><head><title>The Dormouse's story</title></head>
# <body>
# <a class="c1" id="link2" name="ha">i am a2</a>
# <a class="c1" id="i1" name="ha">i am a1</a><i id="it">我是一个新来的</i></body>
# </html>

append在当前标签内部追加一个标签

　　17、insert在当前标签内部指定位置插入一个标签

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

#1、创建一个新标签插入到第二号位置
from bs4.element import Tag
obj = Tag(name='i', attrs={'id': 'it'})
obj.string = '我是一个新来的'
tag = soup.find('body')
tag.insert(2, obj)

print(soup)
# <html><head><title>The Dormouse's story</title></head>
# <body>
# <a class="c1" id="i1" name="ha">i am a1</a>
# <i id="it">我是一个新来的</i>
# <a class="c1" id="link2" name="ha">i am a2</a>
# </body>
# </html>

insert在当前标签内部指定位置插入一个标签

　　18、insert_after,insert_before 在当前标签后面或前面插入

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

from bs4.element import Tag
obj = Tag(name='i', attrs={'id': 'it'})
obj.string = '我是一个新来的'

tag = soup.find('a')
# tag.insert_before(obj)

#1、创建一个i标签，追加到找到的第一个a标签的后面
tag.insert_after(obj)
print(soup)
# <html><head><title>The Dormouse's story</title></head>
# <body>
# <a class="c1" id="i1" name="ha">i am a1</a>
# <i id="it">我是一个新来的</i>
# <a class="c1" id="link2" name="ha">i am a2</a>
# </body>
# </html>

insert_after,insert_before 在当前标签后面或前面插入

　　19、replace_with 将当前标签替换为指定标签

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

#1、使用新创建的i标签替换找到的第一个a标签
from bs4.element import Tag
obj = Tag(name='i', attrs={'id': 'it'})
obj.string = '我是一个新来的'
tag = soup.find('a')
tag.replace_with(obj)    #用我们创建的i标签替换找到的div标签
print(soup)

replace_with 在当前标签替换为指定标签

　　20、wrap，将指定标签把当前标签包裹起来

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

from bs4.element import Tag
obj1 = Tag(name='div', attrs={'id': 'it'})
obj1.string = '我是一个新来的'

#1、创建一个div标签包裹住找到的第一个a标签
tag = soup.find('a')
v = tag.wrap(obj1)    #用创建的div标签包裹找到的a标签
print(soup)
# <html><head><title>The Dormouse's story</title></head>
# <body>
# <div id="it">我是一个新来的<a class="c1" id="i1" name="ha">i am a1</a></div>
# <a class="c1" id="link2" name="ha">i am a2</a>
# </body>
# </html>

wrap，将指定标签把当前标签包裹起来

　　21、unwrap，去掉当前标签，将保留其包裹的标签

html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
    <a class="c1" id="i1" name="ha">i am a1</a>
    <a class="c1" id="link2" name="ha">i am a2</a>
</body>
</html>
"""

from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc, features="lxml")

#1、找到第一个a标签，并去除包裹的标签，所以就只剩下内容了
tag = soup.find('a')
v = tag.unwrap()

print(soup)
# <html><head><title>The Dormouse's story</title></head>
# <body>
# i am a1
# <a class="c1" id="link2" name="ha">i am a2</a>
# </body>
# </html>

unwrap，去掉当前标签，将保留其包裹的标签

　　22、查找某标签的关联标签

tag.find_next(...)
tag.find_all_next(...)
tag.find_next_sibling(...)
tag.find_next_siblings(...)

tag.find_previous(...)
tag.find_all_previous(...)
tag.find_previous_sibling(...)
tag.find_previous_siblings(...)

tag.find_parent(...)
tag.find_parents(...)

# 参数同find_all

查找某标签的关联标签

　　23、select,select_one, CSS选择器

soup.select("title")            #找到title标签
soup.select("p nth-of-type(3)")        
soup.select("body a")            #找到html head 中的title标签
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)

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)

select,select_one, CSS选择器

　　24、标签的内容（不仅可以读还修改）

tag = soup.find('span')        #
print(tag.string)              # 获取span标签中的内容
tag.string = 'new content'     # 将span标签中的内容改成'new content'
print(soup)

tag = soup.find('body')
print(tag.string)
tag.string = 'xxx'
print(soup)

tag = soup.find('body')
v = tag.stripped_strings  # 递归内部获取所有标签的文本
print(v)

标签的内容（不仅可以读还修改）

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原文地址：https://www.cnblogs.com/xiaonq/p/8543116.html