Python爬虫中搜索文档树的方法
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搜索文档树
1.find_all(name, attrs, recursive, text, **kwargs)
1)name参数
name参数可以查找所有名字为name的Tag,字符串对象会被自动忽略掉。
a.传字符串
最简单的过滤器就是字符串,在搜索方法中传入一个字符串参数,Beautiful Soup会查找与字符串完整匹配所有的内容,返回一个列表。
#!/usr/bin/python3 # -*- coding:utf-8 -*- from bs4 import BeautifulSoup html = """The Dormouse's story The Dormouse's story
Once upon a time there were three little sisters; and their names were , Lacie and Tillie; and they lived at the bottom of a well.
...
""" # 创建 Beautiful Soup 对象,指定lxml解析器 soup = BeautifulSoup(html, "lxml") print(soup.find_all("b")) print(soup.find_all("a"))
运行结果
[The Dormouse's story] [, Lacie, Tillie]
B.传正则表达式
如果传入正则表达式作为参数,Beautiful Soup会通过正则表达式match()来匹配内容。
#!/usr/bin/python3 # -*- coding:utf-8 -*- from bs4 import BeautifulSoup import re html = """The Dormouse's story The Dormouse's story
Once upon a time there were three little sisters; and their names were , Lacie and Tillie; and they lived at the bottom of a well.
...
""" # 创建 Beautiful Soup 对象,指定lxml解析器 soup = BeautifulSoup(html, "lxml") for tag in soup.find_all(re.compile("^b")): print(tag.name)
运行结果
body b
C.传列表
如果传入列表参数,Beautiful Soup会将与列表中任一元素匹配的内容以列表方式返回。
#!/usr/bin/python3 # -*- coding:utf-8 -*- from bs4 import BeautifulSoup html = """The Dormouse's story The Dormouse's story
Once upon a time there were three little sisters; and their names were , Lacie and Tillie; and they lived at the bottom of a well.
...
""" # 创建 Beautiful Soup 对象,指定lxml解析器 soup = BeautifulSoup(html, "lxml") print(soup.find_all(['a', 'b']))
2)keyword参数
#!/usr/bin/python3 # -*- coding:utf-8 -*- from bs4 import BeautifulSoup html = """The Dormouse's story The Dormouse's story
Once upon a time there were three little sisters; and their names were , Lacie and Tillie; and they lived at the bottom of a well.
...
""" # 创建 Beautiful Soup 对象,指定lxml解析器 soup = BeautifulSoup(html, "lxml") print(soup.find_all(id="link1"))
运行结果
[]
3)text参数
通过text参数可以搜索文档中的字符串内容,与name参数的可选值一样,text参数接受字符串,正则表达式,列表。
#!/usr/bin/python3 # -*- coding:utf-8 -*- from bs4 import BeautifulSoup import re html = """The Dormouse's story The Dormouse's story
Once upon a time there were three little sisters; and their names were , Lacie and Tillie; and they lived at the bottom of a well.
...
""" # 创建 Beautiful Soup 对象,指定lxml解析器 soup = BeautifulSoup(html, "lxml") # 字符串 print(soup.find_all(text = " Elsie ")) # 列表 print(soup.find_all(text = ["Tillie", " Elsie ", "Lacie"])) # 正则表达式 print(soup.find_all(text = re.compile("Dormouse")))
运行结果
[' Elsie '] [' Elsie ', 'Lacie', 'Tillie'] ["The Dormouse's story", "The Dormouse's story"]
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