python BeautifulSoup库的基本使用
Beautiful Soup 是用Python写的一个HTML/XML的解析器，它可以很好的处理不规范标记并生成剖析树(parse tree)。 它提供简单又常用的导航（navigating），搜索以及修改剖析树的操作。它可以大大节省你的编程时间。
安装
1. 可以利用 pip 或者 easy_install 来安装，以下两种方法均可
easy_install beautifulsoup4 pip install beautifulsoup4
2. 如果想安装最新的版本，请直接下载安装包来手动安装，也是十分方便的方法。
下载地址：https://pypi.python.org/pypi/beautifulsoup4/4.3.2
下载完成之后解压
运行下面的命令即可完成安装
sudo python setup.py install
使用
本文将以下面的HTML代码，讲解使用BeautifulSoup库，bs4库将任何HTML输入都变成utf‐8编码
>>> import requests
>>> r = requests.get('http://python123.io/ws/demo.html')
>>> r.text
'<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>'
>>> demo = r.text
1. BeautifulSoup4库的引用
from bs4 import BeautifulSoup import bs4
2. BeautifulSoup4库解析器
soup = BeautifulSoup('data','html.parser')
| 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 |
3. BeautifulSoup类的基本元素
| 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，字典形式组织，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 |
############## Tag标签 ##############
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo, 'html.parser')
>>> soup.title
<title>This is a python demo page</title>
>>> tag = soup.a
>>> tag
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
任何存在于HTML语法中的标签都可以用soup.<tag>访问获得,当HTML文档中存在多个相同<tag>对应内容时，soup.<tag>返回第一个
############## Tag Name(名字) ##############
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo, 'html.parser')
>>> soup.a.name
'a'
>>> soup.a.parent.name #父级标签名称
'p'
>>> soup.a.parent.parent.name ##父级的父级的标签名称
'body'
每个<tag>都有自己的名字，通过<tag>.name获取，字符串类型
############## Tag attrs(属性) ##############
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo, 'html.parser')
>>> tag = soup.a
>>> tag.attrs
{'class': ['py1'], 'id': 'link1', 'href': 'http://www.icourse163.org/course/BIT-268001'}
>>> tag.attrs['class']
['py1']
>>> tag.attrs['href']
'http://www.icourse163.org/course/BIT-268001'
>>> type(tag.attrs)
<class 'dict'>
>>> type(tag)
<class 'bs4.element.Tag'>
一个<tag>可以有0或多个属性，字典类型
############## Tag的NavigableString ##############
>>> soup.a
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
>>> soup.a.string
'Basic Python'
>>> soup.title
<title>This is a python demo page</title>
>>> soup.title.string
'This is a python demo page'
>>> type(soup.title.string)
<class 'bs4.element.NavigableString'>
NavigableString可以跨越多个层次
############## Tag的Comment ##############
>>> newsoup = BeautifulSoup('<b><!-- This is comment --></b><p>This is comment</p>', 'html.parser')
>>> newsoup.b.string
' This is comment '
>>> type(newsoup.b.string)
<class 'bs4.element.Comment'>
>>> newsoup.p.string
'This is comment'
>>> type(newsoup.p.string)
<class 'bs4.element.NavigableString'>
Comment是一种特殊类型
4. 标签树的遍历
BeautifulSoup类型是标签树的根节点
1）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 |
>>> soup.head
<head><title>This is a python demo page</title></head>
>>> soup.head.contents #返回列表类型
[<title>This is a python demo page</title>]
>>> soup.body.contents
['\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:
<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']
>>> len(soup.body.contents)
5
>>> soup.body.contents[1]
<p class="title"><b>The demo python introduces several python courses.</b></p>
#遍历儿子节点
for child in soup.body.children:
print(child)
#遍历子孙节点
for child in soup.body.descendants:
print(child)
2）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 |
>>> soup.title.parent
<head><title>This is a python demo page</title></head>
>>> soup.html.parent #html的父节点是自己
<html><head><title>This is a python demo page</title></head>
<body>
<p class="title"><b>The demo python introduces several python courses.</b></p>
<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<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>
</body></html>
>>> soup.parent #没有父节点
#标签树的上行遍历(遍历所有先辈节点包括soup本身所以要区别判断)
for parent in soup.a.parents:
if parent is None:
print(parent)
else:
print(parent.name)
3）平行遍历
| 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 |
>>> soup.a.next_sibling ' and ' >>> soup.a.next_sibling.next_sibling <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a> >>> soup.a.previous_sibling 'Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\r\n' #遍历后续节点 for sibling in soup.a.next_sibling: print(sibling) #遍历前续节点 for sibling in soup.a.previous_sibling: print(sibling)
5. 使用prettify方法更友好的输出
>>> import requests
>>> r = requests.get('http://python123.io/ws/demo.html')
>>> r.text
'<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>'
>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(r.text, 'html.parser')
>>> soup.prettify()
'<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>'
>>> print(soup.prettify())
<html>
<head>
<title>
This is a python demo page
</title>
</head>
<body>
<p class="title">
<b>
The demo python introduces several python courses.
</b>
</p>
<p class="course">
Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<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>
</body>
</html>
6. 内容查找
| 方法 | 说明 |
| <>.find() | 搜索且只返回一个结果，同.find_all()参数 |
| <>.find_parents() | 在先辈节点中搜索，返回列表类型，同.find_all()参数 |
| <>.find_parent() | 在先辈节点中返回一个结果，同.find()参数 |
| <>.find_next_siblings() | 在后续平行节点中搜索，返回列表类型，同.find_all()参数 |
| <>.find_next_sibling() | 在后续平行节点中返回一个结果，同.find()参数 |
| <>.find_previous_siblings() | 在前序平行节点中搜索，返回列表类型，同.find_all()参数 |
| <>.find_previous_sibling() | 在前序平行节点中返回一个结果，同.find()参数 |
<>.find_all(name, attrs, recursive, string, **kwargs)
- name : 对标签名称的检索字符串
- attrs: 对标签属性值的检索字符串，可标注属性检索
- recursive: 是否对子孙全部检索，默认True
- string: <>…</>中字符串区域的检索字符串
<tag>(..) 等价于 <tag>.find_all(..)
soup(..) 等价于 soup.find_all(..)
#提取所有URL
for link in soup.find_all('a'):
print(link.get('href'))
http://www.icourse163.org/course/BIT-268001
http://www.icourse163.org/course/BIT-1001870001
>>> soup.find_all('a') #查找所有的a标签，返回一个列表
[<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>, <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>]
>>> soup.find_all(['a','b']) #查找所有的a标签和b标签，返回一个列表
[<b>The demo python introduces several python courses.</b>, <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>, <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>]
>>> soup.find_all('p','course') #查找所有具有course属性的p标签，
[<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<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>]
>>> soup.find_all(id='link1') #查找所有属性为id='link1'的标签
[<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>]
>>> import re #使用正则查找所有id属性中以'link'开头的标签
>>> soup.find_all(id=re.compile('link'))
[<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>, <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>]
>>> soup.find_all('a')
[<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>, <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>]
>>> soup.find_all('a',recursive=False) #查找所有a标签且不遍历子孙节点
[]
>>> soup.find_all(string="Basic Python") #查找所有标签间内容为"Basic Python"的字符串
['Basic Python']
>>> import re
>>> soup.find_all(string=re.compile('python'))
['This is a python demo page', 'The demo python introduces several python courses.'] #查找所有标签间内容中有"python"的字符串
