Python中的BeautifulSoup库简要总结
HuskySir 人气:0一、基本元素
BeautifulSoup库是解析、遍历、维护“标签树”的功能库。
引用
1 from bs4 import BeautifulSoup
1 import bs4
html文档-标签树-BeautifulSoup类
1 from bs4 import BeautifulSoup 2 soup1 = BeautifulSoup(“<html>data</html>”,”html.parser”) 3 soup2 = BeautifulSoup(open(“D:/https://img.qb5200.com/download-x/demo.html”),”html.parser”)
※一个BeautifulSoup对象对应一个HTML/XML文档的全部内容
1 import requests
2 from bs4 import BeautifulSoup 3 r = requests.get("http://python123.io/wshttps://img.qb5200.com/download-x/demo.html") 4 r.text 5 '<html><head><title>This is a python demo page</title></head>\r\n<body>\r\n<p class="title"><b>The demo python introduces several python courses.</b></p>\r\n<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\r\n<a href="http://www.icourse163.org/course/BIT-268001" class="py1" id="link1">Basic Python</a> and <a href="http://www.icourse163.org/course/BIT-1001870001" class="py2" id="link2">Advanced Python</a>.</p>\r\n</body></html>' 6 demo = r.text 7 soup = BeautifulSoup(demo,"html.parser") 8 print(soup.prettify()) 9 <html> 10 <head> 11 <title> 12 This is a python demo page 13 </title> 14 </head> 15 <body> 16 <p class="title"> 17 <b> 18 The demo python introduces several python courses. 19 </b> 20 </p> 20 <p class="course"> 22 Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses: 23 <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1"> 24 Basic Python 25 </a> 26 and 27 <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2"> 28 Advanced Python 29 </a> 30 . 31 </p> 32 </body> 33 </html>
在上述代码中,一个BeautifulSoup对象对应一个HTML文档的全部内容,可查看r,demo,soup的类型
1 type(r) 2 <class 'requests.models.Response'> 3 type(demo) 4 <class 'str'> 5 type(soup) 6 <class 'bs4.BeautifulSoup'>
BeautifulSoup库解析器
解析器 | 使用方法 | 条件 |
bs4的HTML解析器 | BeautifulSoup(mk,’html.parser’) | 安装bs4库 |
lxml的HTML解析器 | BeautifulSoup(mk,’lxml’) | 安装lxml库 |
lxml的XML解析器 | BeautifulSoup(mk,’xml’) | 安装lxml库 |
html5lib的解析器 | BeautifulSoup(mk,’ html5lib’) | 安装html5lib库 |
BeautifulSoup类基本元素
基本元素 | 说明 |
Tag | 标签,最基本的信息组织单元,分别用<>和</>标明开头和结尾 |
Name | 标签的名字,<p>…</p>的名字是’p’,格式:<tag>.name |
Attributes | 标签的属性,字典组织形式,格式:<tag>.attrs |
NavigableString | 标签内非属性字符串,<>…</>中字符串,格式:<tag>.string |
Comment | 标签内字符串的注释部分,一种特殊的Comment类型 |
以"http://python123.io/wshttps://img.qb5200.com/download-x/demo.html"html文档为例,先生成soup对象(BeautifulSoup类),该文档的详细内容在※代码中可看到。
1 import requests
2 from bs4 import BeautifulSoup 3 r = requests.get("http://python123.io/wshttps://img.qb5200.com/download-x/demo.html") 4 demo = r.text 5 soup = BeautifulSoup(demo,"html.parser")
1、soup的标题及标签
文档中有两个a标签,直接使用soup.a只可以获得第一个a标签
1 soup.title #标题 2 <title>This is a python demo page</title> 3 tag = soup.a #标签a 4 tag 5 <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
2、标签名
1 soup.a.name #标签a的标签名 2 'a' 3 soup.a.parent.name #标签a的父标签名 4 'p' 5 soup.a.parent.parent.name #标签a的父标签的父标签名 6 'body'
3、标签属性
1 tag = soup.a #tag为soup中的a标签 2 tag.attrs #标签属性值 3 {'href': 'http://www.icourse163.org/course/BIT-268001', 'class': ['py1'], 'id': 'link1'} 4 tag.attrs['class'] #标签'class'属性值 5 ['py1'] 6 tag.attrs['href'] #标签'href'属性值 7 'http://www.icourse163.org/course/BIT-268001' 8 type(tag.attrs) #标签属性类型 9 <class 'dict'> 10 type(tag) #标签类型 11 <class 'bs4.element.Tag'>
4、标签内非属性字符串
NavigableString可跨越多个层次,如下代码中p标签内还有b标签,但不会打印b标签,而是打印b标签内的字符串
1 soup.a #标签a 2 <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a> 3 soup.a.string #标签a内非属性字符串 4 'Basic Python' 5 soup.p #标签p 6 <p class="title"><b>The demo python introduces several python courses.</b></p> 7 soup.p.string #标签p内非属性字符串 8 'The demo python introduces several python courses.' 9 type(soup.a.string) #标签a内非属性字符串类型 10 <class 'bs4.element.NavigableString'> 11 type(soup.p.string) #标签p内非属性字符串类型 12 <class 'bs4.element.NavigableString'>
5、标签内字符串的注释部分
使用<tag>.string时显示的字符串类型可能是NavigableString,也可能是Comment。
1 newsoup = BeautifulSoup("<b><!-- This is a comment --></b><p>This is not a comment</p>","html.parser") #创建一个新的BeautifulSoup对象 2 newsoup.b.string #标签b的字符串 3 ' This is a comment ' 4 newsoup.p.string #标签p的字符串 5 'This is not a comment' 6 type(newsoup.b.string) #标签b的字符串类型 7 <class 'bs4.element.Comment'> 8 type(newsoup.p.string) #标签p的字符串类型 9 <class 'bs4.element.NavigableString'>
综上所述
<p class = "title">...</p>
标签 .<tag>
名称 .name
属性 .attrs
非属性字符串/注释 .string
二、HTML内容的遍历方法
1、标签树的下行遍历
属性 | 说明 |
.contents | 子节点的列表,将<tag>所有儿子节点存入列表 |
.children | 子节点的迭代类型,与.contents类似,用于循环遍历儿子节点 |
.descendants | 子孙节点的迭代类型,包含所有子孙节点,用于循环遍历 |
以※处的html文档为例
1 import requests 2 from bs4 import BeautifulSoup 3 r = requests.get("http://python123.io/wshttps://img.qb5200.com/download-x/demo.html") 4 demo = r.text 5 soup = BeautifulSoup(demo,"html.parser")
head标签、head标签儿子节点及body标签儿子节点
1 soup.head #head标签 2 <head><title>This is a python demo page</title></head> 3 soup.head.contents #head标签儿子节点 4 [<title>This is a python demo page</title>] 5 soup.body.contents #body标签儿子节点 6 ['\n', <p class="title"><b>The demo python introduces several python courses.</b></p>, '\n', <p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses: 7 <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a> and <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>.</p>, '\n'] 8 len(soup.body.contents) #body标签儿子节点数量 9 5 10 soup.body.contents[1] #body标签中的第二个儿子标签 11 <p class="title"><b>The demo python introduces several python courses.</b></p>
综上
遍历儿子节点
1 for child in soup.body.children: 2 print(child)
遍历子孙节点
for descendant in soup.body.descendants print(child)
2、标签树的上行遍历
属性 | 说明 |
.parent | 节点的父亲标签 |
.parents | 节点先辈标签的迭代类型,用于循环遍历先辈节点 |
同样的,以※处的html文档为例
1 soup.title.parent #title的父标签 2 <head><title>This is a python demo page</title></head> 3 soup.html.parent #html的父标签 4 <html><head><title>This is a python demo page</title></head> 5 <body> 6 <p class="title"><b>The demo python introduces several python courses.</b></p> 7 <p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses: 8 <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a> and <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>.</p> 9 </body></html> 10 soup.parent #soup的父标签
由以上代码可知,title标签的父标签为head标签,html标签是html文档的最高级标签,其父标签就是自己。soup是一种特殊的标签,其父标签为空。
标签树的上行遍历
1 soup = BeautifulSoup(demo,"html.parser") 2 for parent in soup.a.parents: 3 if parent is None: 4 print(parent) 5 else: 6 print(parent.name)
3、标签树的平行遍历
平行遍历发生在同一个父节点下的各节点间
属性 | 说明 |
.next_sibling | 返回按照HTML文本顺序的下一个平行节点标签 |
.previous_sibling | 返回按照HTML文本顺序的上一个平行节点标签 |
.next_siblings | 迭代类型,返回按照HTML文本顺序的后续所有平行节点标签 |
.previous_siblings | 迭代类型,返回按照HTML文本顺序的前续所有平行节点标签 |
同样的,以※处的html文档为例
1 soup.a.next_sibling #标签a的后续平行节点 2 ' and ' 3 soup.a.next_sibling.next_sibling #标签a后续平行节点的后续平行节点 4 <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a> 5 soup.a.previous_sibling #标签a的前续平行节点 6 'Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\r\n' 7 soup.a.previous_sibling.previous_sibling #标签a前续平行节点的前续平行节点(为空) 8 soup.a.parent #标签a的父亲节点 9 <p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses: 10 <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a> and <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>.</p>
遍历后续节点
1 for sibling in soup.a.next_siblings: 2 print(sibling)
遍历前续节点
1 for sibling in soup.a.previous_siblings: 2 print(sibling)
三、HTML的格式化和编码
prettify()方法
以※处的html文档为例
1 soup.prettify() 2 '<html>\n <head>\n <title>\n This is a python demo page\n </title>\n </head>\n <body>\n <p class="title">\n <b>\n The demo python introduces several python courses.\n </b>\n </p>\n <p class="course">\n Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\n <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">\n Basic Python\n </a>\n and\n <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">\n Advanced Python\n </a>\n .\n </p>\n </body>\n</html>' 3 print(soup.prettify()) 4 <html> 5 <head> 6 <title> 7 This is a python demo page 8 </title> 9 </head> 10 <body> 11 <p class="title"> 12 <b> 13 The demo python introduces several python courses. 14 </b> 15 </p> 16 <p class="course"> 17 Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses: 18 <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1"> 19 Basic Python 20 </a> 21 and 22 <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2"> 23 Advanced Python 24 </a> 25 . 26 </p> 27 </body> 28 </html>
编码方式为utf-8
资料来源:北京理工大学,嵩天,Mooc
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