Beautifulsoup - 润新知

Beautifulsoup
Beautiful Soup：解析HTML页面信息标记与提取方法

获取网页源代码
```
import requests
from bs4 import BeautifulSoup

kv = {'user-agent':'Mozilla/5.0'}
url = "https://python123.io/ws/demo.html"
r = requests.get(url,headers = kv)
print(r.status_code)
demo = r.text
soup = BeautifulSoup(demo,"html.parser")#解析
print(soup.prettify())
```
200
<html><head><title>This is a python demo page</title></head>
<body>
The demo python introduces several python courses.
Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<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>.
</body></html>

<html>
<head>
<title>
This is a python demo page
</title>
</head>
<body>


The demo python introduces several python courses.



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>
.

</body>
</html>

BeautifulSoup的使用

BeautifulSoup库解析器

BeautifulSoup类的基本元素
```
https://python123.io/ws/demo.html
```
```
import requests
from bs4 import BeautifulSoup
kv = {'user-agent':'Mozilla/5.0'}
url = "https://python123.io/ws/demo.html"
r = requests.get(url,headers = kv)
print(r.status_code)
demo = r.text
soup = BeautifulSoup(demo,"html.parser")
print(soup.title)
tag = soup.a#只能返回一个a标签
print(tag)
```
200
<title>This is a python demo page</title>
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
```
print(soup.a.name)
print(soup.a.parent.name)
print(soup.a.parent.parent.name)
```
a
p
body
```
print(tag.attrs['href'])
print(type(tag.attrs))字典
print(type(tag))
```
{'href': 'http://www.icourse163.org/course/BIT-268001', 'class': ['py1'], 'id': 'link1'}
http://www.icourse163.org/course/BIT-268001
<class 'dict'>
<class 'bs4.element.Tag'>
```
tag = soup.a
print(tag)
print(tag.string)
tag1 = soup.p
print(tag1)
print(tag1.string)
tag2 = soup.b
print(tag2)
print(tag2.string)
```
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
Basic Python
The demo python introduces several python courses.
The demo python introduces several python courses.
The demo python introduces several python courses.
The demo python introduces several python courses.
```
print(type(tag2.string))
```
<class 'bs4.element.NavigableString'>
```
soup = BeautifulSoup("This is not a comment","html.parser")
print(soup.b.string)
print(type(soup.b.string))
print(soup.p.string)
print(type(soup.p.string))
```
This is a comment
<class 'bs4.element.Comment'>
This is not a comment
<class 'bs4.element.NavigableString'>

基于bs4库的HTML内容遍历方法

<html>
<head>
<title>
This is a python demo page
</title>
</head>
<body>


The demo python introduces several python courses.



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>
.

</body>
</html>

上述的标签树如下

三种遍历方式

下行遍历
```
soup = BeautifulSoup(demo,"html.parser")
print(soup.head)
print(soup.head.contents)
print(soup.body.contents)返回列表
print(len(soup.body.contents))
print(soup.body.contents[1])
```
<head><title>This is a python demo page</title></head>
[<title>This is a python demo page</title>]
[' ', The demo python introduces several python courses., ' ', Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the foll
owing 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>., ' ']
5
The demo python introduces several python courses.
```
for child in soup.body.children:
 print(child) # 遍历儿子节点 
```
The demo python introduces several python courses.

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>.
```
for child in soup.body.descendants:
 print(child) # 遍历子孙节点
```
The demo python introduces several python courses.
The demo python introduces several python courses.
The demo python introduces several python courses.

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>.
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>
Basic Python
and
<a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>
Advanced Python
.
```
上行遍历
```
```
for parent in soup.a.parents: # 遍历soup的a标签的先辈标签
 if parent is None:
 print(parent)
 else:
 print(parent.name)
```
p
body
html
[document]
```
soup = BeautifulSoup(demo,"html.parser")
tag = soup.a
print(tag)
print(tag.parent)
```
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
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>.

强调：soup.html的parent是它本身 soup.parent是空的
```
for parent in soup.a.parents: # 遍历soup的a标签的先辈标签
 if parent is None:
 print( parent)
 else:
 print(parent.name)
```
p
body
html
[document]

平行遍历
```
平行遍历发生在同一父节点的各节点间
```
```
标签间的NavigableString也会构成标签树的节点，那么某个节点的父节点、子节点或者平行标签都有可能是NavigableString类型的
```
```
soup = BeautifulSoup(demo,"html.parser")
tag = soup.a
print(tag.next_sibling)
print(tag.next_sibling.next_sibling)
print(tag.previous_sibling)
print(tag.previous_sibling.previous_sibling)
```
```
print(tag.parent)
```
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>.

and
<a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>
.

Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:

基于bs4库的HTML格式输出
```
soup = BeautifulSoup(demo,"html.parser")
print(soup.prettify())#在每个标签后面加了一个换行符，便于美观的输出
```
```
bs4的编码默认都为utf-8编码
```
```
soup = BeautifulSoup("你好","html.parser")
print(soup.p.string)
print(soup.p.prettify())
```
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原文地址：https://www.cnblogs.com/tingtin/p/12907452.html