#BeautifulSoup模块简介和安装
from bs4 import BeautifulSoup
import re
#CSS 选择器：BeautifulSoup4
#和lxml 一样，Beautiful Soup 也是一个HTML/XML的解析器
#主要的功能也是如何解析和提取 HTML/XML 数据。
#模块下载安装：pip install bs4
#基础例子
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>
"""
#解析字符串形式的html
soup=BeautifulSoup(html,"lxml")
# #解析本地html文件
# soup2=BeautifulSoup(open("index.html"))
#格式化输出soup对象
#print(soup.prettify())
# #根据标签名获取标签信息 soup.标签名
# print(soup.title)
# #获取标签内容
# print(soup.title.string)
# #获取标签名
# print(soup.title.name)
# #获取标签内所有属性
# print(soup.p.attrs["name"])
#获取标签内子标签，结果是一个列表
#print(soup.head.contents)
#获取标签内子标签，结果是一个生成器
# print(soup.head.children)
# for i in soup.head.children:
# print(i)
#获取所有子标签
# print(soup.p.descendants)
# for i in soup.p.descendants:
# print(i)
#搜索文档树 fild
#根据字符串查找所有的a标签，返回一个结果集，里面装的是标签对象
# data=soup.find_all("a")
# for i in data:
# print(i.string)
#根据正则表达式查找标签
# data2=soup.find_all(re.compile("^b"))
# for i in data2:
# print(i.string)
#根据属性查找标签
# data3=soup.find_all(id="link2")
# for i in data3:
# print(i)
#根据标签内容获取标签内容
# data4=soup.find_all(text="Lacie")
# data5=soup.find_all(text=["Lacie","Tillie"])
# data6=soup.find_all(text=re.compile("Do"))
# print(data6)
#CSS选择器 select()
#根据CSS样式表来查找标签
#CSS选择器内容：标签选择器，类选择器，id选择器
# #通过标签名获取标签
# data=soup.select("a")
#通过类名查找
#data=soup.select(".sister")
#通过id查找
#data=soup.select("#link2")
#组合查找
#data=soup.select("p #link1")
#通过其他属性查找
data=soup.select('a[href="http://example.com/elsie"]')
print(data)
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