Python爬虫之BeautifulSoup的基本使用教程
目录
- bs4的安装
- bs4的快速入门
- 解析器的比较(了解即可)
- 对象种类
- bs4的简单使用
- 获取标签内容
- 获取标签名字
- 获取a标签的href属性值
- 遍历文档树
- 案例练习
- 思路
- 代码实现
- 总结
bs4的安装
要使用BeautifulSoup4需要先安装lxml,再安装bs4
pip install lxml
pip install bs4
使用方法:
from bs4 import BeautifulSoup
lxml和bs4对比学习
from lxml import etree tree = etree.HTML(html) tree.xpath()
from bs4 import BeautifulSoup soup = BeautifulSoup(html_doc, 'lxml')
注意事项:
创建soup对象时如果不传’lxml’或者features="lxml"会出现以下警告
bs4的快速入门
解析器的比较(了解即可)
解析器 | 用法 | 优点 | 缺点 |
---|---|---|---|
python标准库 | BeautifulSoup(markup,‘html.parser’) | python标准库,执行速度适中 | (在python2.7.3或3.2.2之前的版本中)文档容错能力差 |
lxml的HTML解析器 | BeautifulSoup(markup,‘lxml’) | 速度快,文档容错能力强 | 需要安装c语言库 |
lxml的XML解析器 | BeautifulSoup(markup,‘lxml-xml’)或者BeautifulSoup(markup,‘xml’) | 速度快,唯一支持XML的解析器 | 需要安装c语言库 |
html5lib | BeautifulSoup(markup,‘html5lib’) | 最好的容错性,以浏览器的方式解析文档,生成HTML5格式的文档 | 速度慢,不依赖外部扩展 |
对象种类
Tag:标签
BeautifulSoup:bs对象
NavigableString:可导航的字符串
Comment:注释
from bs4 import BeautifulSoup # 创建模拟HTML代码的字符串 html_doc = """ <html><head><title>The Dormouse's story</title></head> <body> <p class="title"><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> <span><!--comment注释内容举例--></span> """ # 创建soup对象 soup = BeautifulSoup(html_doc, 'lxml') print(type(soup.title)) # <class 'bs4.element.Tag'> print(type(soup)) # <class 'bs4.BeautifulSoup'> print(type(soup.title.string)) # <class 'bs4.element.NavigableString'> print(type(soup.span.string)) # <class 'bs4.element.Comment'>
bs4的简单使用
获取标签内容
from bs4 import BeautifulSoup # 创建模拟HTML代码的字符串 html_doc = """ <html><head><title>The Dormouse's story</title></head> <body> <p class="title"><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> </body> </html> """ # 创建soup对象 soup = BeautifulSoup(html_doc, 'lxml') print('head标签内容:\n', soup.head) # 打印head标签 print('body标签内容:\n', soup.body) # 打印body标签 print('html标签内容:\n', soup.html) # 打印html标签 print('p标签内容:\n', soup.p) # 打印p标签
注意:在打印p标签对应的代码时,可以发现只打印了第一个p标签内容,这时我们可以通过find_all来获取p标签全部内容
print('p标签内容:\n', soup.find_all('p'))
这里需要注意使用find_all里面必须传入的是字符串
获取标签名字
通过name属性获取标签名字
from bs4 import BeautifulSoup # 创建模拟HTML代码的字符串 html_doc = """ <html><head><title>The Dormouse's story</title></head> <body> <p class="title"><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> </body> </html> """ # 创建soup对象 soup = BeautifulSoup(html_doc, 'lxml') print('head标签名字:\n', soup.head.name) # 打印head标签名字 print('body标签名字:\n', soup.body.name) # 打印body标签名字 print('html标签名字:\n', soup.html.name) # 打印html标签名字 print('p标签名字:\n', soup.find_all('p').name) # 打印p标签名字
如果要找到两个标签的内容,需要传入列表过滤器,而不是字符串过滤器
使用字符串过滤器获取多个标签内容会返回空列表
print(soup.find_all('title', 'p'))
[]
需要使用列表过滤器获取多个标签内容
print(soup.find_all(['title', 'p']))
[<title>The Dormouse's story</title>, <p class="title"><b>The Dormouse's story</b></p>, <p class="story">Once upon a time there were three little sisters; and their names were
<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a> and
<a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>, <p class="story">...</p>]
获取a标签的href属性值
from bs4 import BeautifulSoup # 创建模拟HTML代码的字符串 html_doc = """ <html><head><title>The Dormouse's story</title></head> <body> <p class="title"><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> """ # 创建soup对象 soup = BeautifulSoup(html_doc, 'lxml') a_list = soup.find_all('a') # 遍历列表取属性值 for a in a_list: # 第一种方法通过get去获取href属性值(没有找到返回None) print(a.get('href')) # 第二种方法先通过attrs获取所有属性值,再提取出你想要的属性值 print(a.attrs['href']) # 第三种方法获取没有的属性值会报错 print(a['href'])
扩展:使用prettify()美化 让节点层级关系更加明显 方便分析
print(soup.prettify())
不使用prettify时的代码
<html><head><title>The Dormouse's story</title></head> <body> <p class="title"><b>The Dormouse's story</b></p> <p class="story">Once upon a time there were three little sisters; and their names were <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>, <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a> and <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>; and they lived at the bottom of a well.</p> <p class="story">...</p> </body></html>
遍历文档树
from bs4 import BeautifulSoup # 创建模拟HTML代码的字符串 html_doc = """ <html><head><title>The Dormouse's story</title></head> <body> <p class="title"><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> </body> </html> """ soup = BeautifulSoup(html_doc, 'lxml') head = soup.head # contents返回的是所有子节点的列表 [<title>The Dormouse's story</title>] print(head.contents) # children返回的是一个子节点的迭代器 <list_iterator object at 0x00000264BADC2748> print(head.children) # 凡是迭代器都是可以遍历的 for h in head.children: print(h) html = soup.html # 会把换行也当作子节点匹配到 # descendants 返回的是一个生成器遍历子子孙孙 <generator object Tag.descendants at 0x0000018C15BFF4C8> print(html.descendants) # 凡是生成器都是可遍历的 for h in html.descendants: print(h) ''' 需要重点掌握的 string获取标签里面的内容 strings 返回是一个生成器对象用过来获取多个标签内容 stripped_strings 和strings基本一致 但是它可以把多余的空格去掉 ''' print(soup.title.string) print(soup.html.string) # 返回生成器对象<generator object Tag._all_strings at 0x000001AAFF9EF4C8> # soup.html.strings 包含在html标签里面的文本都会被获取到 print(soup.html.strings) for h in soup.html.strings: print(h) # stripped_strings可以把多余的空格去掉 # 返回生成器对象<generator object PageElement.stripped_strings at 0x000001E31284F4C8> print(soup.html.stripped_strings) for h in soup.html.stripped_strings: print(h) ''' parent直接获得父节点 parents获取所有的父节点 ''' title = soup.title # parent找直接父节点 print(title.parent) # parents获取所有父节点 # 返回生成器对象<generator object PageElement.parents at 0x000001F02049F4C8> print(title.parents) for p in title.parents: print(p) # html的父节点就是整个文档 print(soup.html.parent) # <class 'bs4.BeautifulSoup'> print(type(soup.html.parent))
案例练习
获取所有职位名称
html = """ <table class="tablelist" cellpadding="0" cellspacing="0"> <tbody> <tr class="h"> <td class="l" width="374">职位名称</td> <td>职位类别</td> <td>人数</td> <td>地点</td> <td>发布时间</td> </tr> <tr class="even"> <td class="l square"><a target="_blank" href="position_detail.php?id=33824&keywords=python&tid=87&lid=2218">22989-金融云区块链高级研发工程师(深圳)</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-25</td> </tr> <tr class="odd"> <td class="l square"><a target="_blank" href="position_detail.php?id=29938&keywords=python&tid=87&lid=2218">22989-金融云高级后台开发</a></td> <td>技术类</td> <td>2</td> <td>深圳</td> <td>2017-11-25</td> </tr> <tr class="even"> <td class="l square"><a target="_blank" href="position_detail.php?id=31236&keywords=python&tid=87&lid=2218">SNG16-腾讯音乐运营开发工程师(深圳)</a></td> <td>技术类</td> <td>2</td> <td>深圳</td> <td>2017-11-25</td> </tr> <tr class="odd"> <td class="l square"><a target="_blank" href="position_detail.php?id=31235&keywords=python&tid=87&lid=2218">SNG16-腾讯音乐业务运维工程师(深圳)</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-25</td> </tr> <tr class="even"> <td class="l square"><a target="_blank" href="position_detail.php?id=34531&keywords=python&tid=87&lid=2218">TEG03-高级研发工程师(深圳)</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-24</td> </tr> <tr class="odd"> <td class="l square"><a target="_blank" href="position_detail.php?id=34532&keywords=python&tid=87&lid=2218">TEG03-高级图像算法研发工程师(深圳)</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-24</td> </tr> <tr class="even"> <td class="l square"><a target="_blank" href="position_detail.php?id=31648&keywords=python&tid=87&lid=2218">TEG11-高级AI开发工程师(深圳)</a></td> <td>技术类</td> <td>4</td> <td>深圳</td> <td>2017-11-24</td> </tr> <tr class="odd"> <td class="l square"><a target="_blank" href="position_detail.php?id=32218&keywords=python&tid=87&lid=2218">15851-后台开发工程师</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-24</td> </tr> <tr class="even"> <td class="l square"><a target="_blank" href="position_detail.php?id=32217&keywords=python&tid=87&lid=2218">15851-后台开发工程师</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-24</td> </tr> <tr class="odd"> <td class="l square"><a id="test" class="test" target='_blank' href="position_detail.php?id=34511&keywords=python&tid=87&lid=2218">SNG11-高级业务运维工程师(深圳)</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-24</td> </tr> </tbody> </table> """
思路
不难看出想要的数据在tr节点的a标签里,只需要遍历所有的tr节点,从遍历出来的tr节点取a标签里面的文本数据
代码实现
from bs4 import BeautifulSoup html = """ <table class="tablelist" cellpadding="0" cellspacing="0"> <tbody> <tr class="h"> <td class="l" width="374">职位名称</td> <td>职位类别</td> <td>人数</td> <td>地点</td> <td>发布时间</td> </tr> <tr class="even"> <td class="l square"><a target="_blank" href="position_detail.php?id=33824&keywords=python&tid=87&lid=2218">22989-金融云区块链高级研发工程师(深圳)</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-25</td> </tr> <tr class="odd"> <td class="l square"><a target="_blank" href="position_detail.php?id=29938&keywords=python&tid=87&lid=2218">22989-金融云高级后台开发</a></td> <td>技术类</td> <td>2</td> <td>深圳</td> <td>2017-11-25</td> </tr> <tr class="even"> <td class="l square"><a target="_blank" href="position_detail.php?id=31236&keywords=python&tid=87&lid=2218">SNG16-腾讯音乐运营开发工程师(深圳)</a></td> <td>技术类</td> <td>2</td> <td>深圳</td> <td>2017-11-25</td> </tr> <tr class="odd"> <td class="l square"><a target="_blank" href="position_detail.php?id=31235&keywords=python&tid=87&lid=2218">SNG16-腾讯音乐业务运维工程师(深圳)</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-25</td> </tr> <tr class="even"> <td class="l square"><a target="_blank" href="position_detail.php?id=34531&keywords=python&tid=87&lid=2218">TEG03-高级研发工程师(深圳)</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-24</td> </tr> <tr class="odd"> <td class="l square"><a target="_blank" href="position_detail.php?id=34532&keywords=python&tid=87&lid=2218">TEG03-高级图像算法研发工程师(深圳)</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-24</td> </tr> <tr class="even"> <td class="l square"><a target="_blank" href="position_detail.php?id=31648&keywords=python&tid=87&lid=2218">TEG11-高级AI开发工程师(深圳)</a></td> <td>技术类</td> <td>4</td> <td>深圳</td> <td>2017-11-24</td> </tr> <tr class="odd"> <td class="l square"><a target="_blank" href="position_detail.php?id=32218&keywords=python&tid=87&lid=2218">15851-后台开发工程师</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-24</td> </tr> <tr class="even"> <td class="l square"><a target="_blank" href="position_detail.php?id=32217&keywords=python&tid=87&lid=2218">15851-后台开发工程师</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-24</td> </tr> <tr class="odd"> <td class="l square"><a id="test" class="test" target='_blank' href="position_detail.php?id=34511&keywords=python&tid=87&lid=2218">SNG11-高级业务运维工程师(深圳)</a></td> <td>技术类</td> <td>1</td> <td>深圳</td> <td>2017-11-24</td> </tr> </tbody> </table> """ # 创建soup对象 soup = BeautifulSoup(html, 'lxml') # 使用find_all()找到所有的tr节点(经过观察第一个tr节点为表头,忽略不计) tr_list = soup.find_all('tr')[1:] # 遍历tr_list取a标签里的文本数据 for tr in tr_list: a_list = tr.find_all('a') print(a_list[0].string)
运行结果如下:
22989-金融云区块链高级研发工程师(深圳)
22989-金融云高级后台开发
SNG16-腾讯音乐运营开发工程师(深圳)
SNG16-腾讯音乐业务运维工程师(深圳)
TEG03-高级研发工程师(深圳)
TEG03-高级图像算法研发工程师(深圳)
TEG11-高级AI开发工程师(深圳)
15851-后台开发工程师
15851-后台开发工程师
SNG11-高级业务运维工程师(深圳)
总结
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