bs4

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一、
bs4安装与使用

‘‘‘‘‘‘
‘‘‘
安装解析器:
pip3 install lxml

安装解析库:
pip3 install bs4
‘‘‘
html_doc = """
<html><head><title>The Dormouse‘s story</title></head>
<body>
<p class="sister"><b>$37</b></p>
<p class="story" id="p">Once upon a time there were three little sisters; and their names were
<a href="http://example.com/elsie" class="sister" >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

# python自带的解析库
# soup = BeautifulSoup(html_doc, ‘html.parser‘)

# 调用bs4得到一个soup对象
soup = BeautifulSoup(html_doc, ‘lxml‘)

# bs4对象
print(soup)

# bs4类型
print(type(soup))

# 美化功能
html = soup.prettify()
print(html)
二、bs4解析库之遍历文档树

‘‘‘‘‘‘
‘‘‘
安装解析器:
pip3 install lxml

安装解析库:
pip3 install bs4
‘‘‘
html_doc = """
<html><head><title>The Dormouse‘s story</title></head>
<body>
<p class="sister"><b>$37</b></p>
<p class="story" id="p">Once upon a time there were three little sisters; and their names were
<a href="http://example.com/elsie" class="sister" >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

# python自带的解析库
# soup = BeautifulSoup(html_doc, ‘html.parser‘)

# 调用bs4得到一个soup对象
soup = BeautifulSoup(html_doc, ‘lxml‘)

# bs4对象
print(soup)

# bs4类型
print(type(soup))

# 美化功能
html = soup.prettify()
print(html)

三、bs4解析库之遍历文档树
html_doc = """
<html><head><title>The Dormouse‘s story</title></head>
<body>
<p class="sister"><b>$37</b></p>
<p class="story" id="p">Once upon a time there were three little sisters; and their names were
<a href="http://example.com/elsie" class="sister" >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_doc, ‘lxml‘)
# print(soup)
# print(type(soup))
# 遍历文档树
# 1、直接使用  *****
print(soup.html)
print(type(soup.html))
print(soup.a)
print(soup.p)

# 2、获取标签的名称
print(soup.a.name)

# 3、获取标签的属性   *****
print(soup.a.attrs)  # 获取a标签中所有的属性
print(soup.a.attrs[‘href‘])

# 4、获取标签的文本内容  *****
print(soup.p.text)  # $37

# 5、嵌套选择
print(soup.html.body.p)

# 6、子节点、子孙节点
print(soup.p.children)  # 返回迭代器对象
print(list(soup.p.children))  # [<b>$37</b>]

# 7、父节点、祖先节点
print(soup.b.parent)
print(soup.b.parents)
print(list(soup.b.parents))

# 8、兄弟节点  （sibling: 兄弟姐妹）
print(soup.a)
# 获取下一个兄弟节点
print(soup.a.next_sibling)

# 获取下一个的所有兄弟节点,返回的是一个生成器
print(soup.a.next_siblings)
print(list(soup.a.next_siblings))

# 获取上一个兄弟节点
print(soup.a.previous_sibling)
# 获取上一个的所有兄弟节点，返回的是一个生成器
print(list(soup.a.previous_siblings))

四、bs4之搜索文档树
‘‘‘‘‘‘
‘‘‘
find: 找第一个
find_all: 找所有

标签查找与属性查找:
name 属性匹配

    name 标签名
    attrs 属性查找匹配
    text 文本匹配
            
    标签:
        - 字符串过滤器   
            字符串全局匹配
            
        - 正则过滤器
            re模块匹配
            
        - 列表过滤器
            列表内的数据匹配
            
        - bool过滤器
            True匹配
            
        - 方法过滤器
            用于一些要的属性以及不需要的属性查找。
    属性:
        - class_
        - id
‘‘‘
html_doc = """
<html><head><title>The Dormouse‘s story</title></head><body><p class="sister"><b>$37</b></p><p class="story" id="p">Once upon a time there were three little sisters; and their names were<a href="http://example.com/elsie" class="sister" >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_doc, ‘lxml‘)

# name 标签名
# attrs 属性查找匹配
# text 文本匹配
# find与find_all搜索文档

‘‘‘

字符串过滤器
‘‘‘
p = soup.find(name=‘p‘)
p_s = soup.find_all(name=‘p‘)

print(p)
print(p_s)

# name + attrs
p = soup.find(name=‘p‘, attrs="id": "p")
print(p)

# name + text
tag = soup.find(name=‘title‘, text="The Dormouse‘s story")
print(tag)

# name + attrs + text
tag = soup.find(name=‘a‘, attrs="class": "sister", text="Elsie")
print(tag)

‘‘‘
- 正则过滤器
re模块匹配
‘‘‘
import re
# name
# 根据re模块匹配带有a的节点
a = soup.find(name=re.compile(‘a‘))
print(a)

a_s = soup.find_all(name=re.compile(‘a‘))
print(a_s)


# attrs
a = soup.find(attrs="id": re.compile(‘link‘))
print(a)


# - 列表过滤器
# 列表内的数据匹配
print(soup.find(name=[‘a‘, ‘p‘, ‘html‘, re.compile(‘a‘)]))
print(soup.find_all(name=[‘a‘, ‘p‘, ‘html‘, re.compile(‘a‘)]))


# - bool过滤器
# True匹配
print(soup.find(name=True, attrs="id": True))

# - 方法过滤器
# 用于一些要的属性以及不需要的属性查找。

def have_id_not_class(tag):
    # print(tag.name)
    if tag.name == ‘p‘ and tag.has_attr("id") and not tag.has_attr("class"):
        return tag

# print(soup.find_all(name=函数对象))
print(soup.find_all(name=have_id_not_class))


# 补充知识点:
# id
a = soup.find(id=‘link2‘)
print(a)

# class
p = soup.find(class_=‘sister‘)
print(p)



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