day03.2 bs4安装与使用、 bs4解析库之遍历文档树、bs4之搜索文档树

- 日理万妓 2021-11-09 11:46 302阅读 0赞

**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>
 $37
 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.
 
 ...
 """
 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)

**bs4解析库之遍历文档树**

html_doc = """
 <html><head><title>The Dormouse's story</title></head>
 <body>
 $37
 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.
 
 ...
 """
 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)) # [$37]
 
 # 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))

**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>$37Once 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....
 """
 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)

转载于:https://www.cnblogs.com/jiangbaoyabo/p/11129776.html