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Python BeautifulSoup使用

hacker707 人气:0

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
html5libBeautifulSoup(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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