Python Beautiful Soup库简单讲解--包括安装
Beautiful Soup库入门
本文是Mooc上 Python网络爬虫与信息提取 的笔记
1 Beautiful Soup库的安装
这里以PyCharm为例(因为我用的就是这种方法)
点击的顺序为
File->Settings->Project:Pycharm->Python Interperter->
然后点击右上角的加号.添加我们想要加入的库
2 Beautiful Soup库的基本元素
一个HTML文件是由一组<>构成的标签组成的
Beautiful Soup库就是用来处理这些标签的
..
: 标签 Tag
…
名称 Name 属性 Attributes
成对出现 0个或者多个
Beautiful Soup库的引用
Beautiful Soup库，也叫 beautifulsoup4或者bs4
引用方式如下
from bs4 import BeautifulSoup
HTML文档 标签树 BeautifulSoup 是相等的
BeautifulSoup对应一个HTML/XML文档的全部内容
BeautifulSoup库的解析器
soup = BeautifulSoup(‘data’，‘html.parser’)
‘html.parser’ 就是更改的内容
| 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’) | pip install lxml |
| lxml的XML解析器 | BeautifulSoup(mk,‘xml’) | pip install lxml |
| html5lib的解析器 | BeautifulSoup(mk,‘html5lib’) | pip install html5lib |
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， … 的名字是’p’，格式：.name |
| Attributes | 标签的属性，字典形式组织，格式：.attrs |
| NavigableString | 标签内非属性字符串，<>…中字符串，格式：.string |
| Comment | 标签内字符串的注释部分，一种特殊的Comment类型 |
一堆例子
Tag的使用
import requests
from bs4 import BeautifulSoup
r = requests.get('http://python123.io/ws/demo.html')
demo = r.text #获取到url 地点的源码
soup = BeautifulSoup(demo,'html.parser')
print(soup.title) #输出title标签的内容
结果如下
This is a python demo page
查看标签的名字
import requests
from bs4 import BeautifulSoup
r = requests.get('http://python123.io/ws/demo.html')
demo = r.text #获取到url 地点的源码
soup = BeautifulSoup(demo,'html.parser')
print(soup.a.name) #输出a标签的名字
print(soup.a.parent.name) #输出a标签的父标签的名字
print(soup.a.parent.parent.name) #输出a标签的父标签的父标签的名字
结果如下
a
p
body
标签的属性信息
import requests
from bs4 import BeautifulSoup
r = requests.get('http://python123.io/ws/demo.html')
demo = r.text #获取到url 地点的源码
soup = BeautifulSoup(demo,'html.parser')
tag = soup.a
print(tag.attrs) #输出a标签的属性
print(tag.attrs['class']) #输出a标签中的class属性
print(tag.attrs['href']) #输出a标签的链接属性
print(type(tag.attrs)) #输出a属性的类型
print(type(tag)) #输出标签的类型(返回的是一个字典)
结果如下
{'href': 'http://www.icourse163.org/course/BIT-268001', 'class': ['py1'], 'id': 'link1'}
['py1']
http://www.icourse163.org/course/BIT-268001
NavigableString元素的处理
import requests
from bs4 import BeautifulSoup
r = requests.get('http://python123.io/ws/demo.html')
demo = r.text #获取到url 地点的源码
soup = BeautifulSoup(demo,'html.parser')
print(soup.a)
print(soup.a.string) #查办a标签中的字符串
print(soup.p)
print(soup.p.string) #查看p标签中的字符串
print(type(soup.p.string)) #查看p标签中的字符串的类型
结果如下
Basic Python
Basic Python
The demo python introduces several python courses.
The demo python introduces several python courses.
关于注释
import requests
from bs4 import BeautifulSoup
newsoup = BeautifulSoup('This is not a comment
','html.parser')
print(newsoup.b.string)
print(type(newsoup.b.string))
print(newsoup.p.string)
print(type(newsoup.p.string))
结果如下
This is a comment
This is not a comment
3 基于bs4库的HTML内容遍历方法
回顾demo的例子
import requests
r = requests.get('http://python123.io/ws/demo.html')
demo = r.text
print(demo)
结果如下:
This is a python demo page
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:
Basic Python and Advanced Python.
HTML的基本格式可以分为一个树形结构
标签树的下行遍历
BeautifulSoup类型是标签树的根节点
| 属性 | 说明 |
|---|---|
| .contents | 子节点的列表，将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 |
学习代码如下
import requests
from bs4 import BeautifulSoup
r = requests.get('http://python123.io/ws/demo.html')
demo = r.text
soup = BeautifulSoup(demo,'html.parser')
print(soup.head)
print(soup.head.contents) #.contents返回的类型是列表
print(soup.body.contents)
print(len(soup.body.contents)) #输出body结点的个数
print(soup.body.contents[1]) #输出body结点的第二个
for child in soup.body.children: #遍历儿子节点
print(child)
for child in soup.body.descendants: #遍历子孙节点
print(child)
输出结果如下
This is a python demo page
[This is a python demo page ]
['\n', The demo python introduces several python courses.
, '\n', Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
Basic Python and Advanced Python.
, '\n']
5
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:
Basic Python and Advanced Python.
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:
Basic Python and Advanced Python.
Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
Basic Python
Basic Python
and
Advanced Python
Advanced Python
.
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 |
学习代码
import requests
from bs4 import BeautifulSoup
r = requests.get('http://python123.io/ws/demo.html')
demo = r.text
soup = BeautifulSoup(demo,'html.parser')
for parent in soup.a.parents:
if parent is None: #他的父亲结点可能是空的,所以要加上这样的一句
print(parent)
else:
print(parent.name)
结果如下
p
body
html
[document]
标签树的平行遍历
| 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 |
平行遍历发生再同一个父结点下的各节点间
import requests
from bs4 import BeautifulSoup
r = requests.get('http://python123.io/ws/demo.html')
demo = r.text
soup = BeautifulSoup(demo,'html.parser')
for sibling in soup.a.next_siblings: #遍历后续结点
print(sibling)
for sibling in soup.a.previous_siblings: #遍历
print(sibling)
结果如下
and
Advanced Python
.
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
bs4库的prettify()方法
import requests
from bs4 import BeautifulSoup
r = requests.get('http://python123.io/ws/demo.html')
demo = r.text
soup = BeautifulSoup(demo,'html.parser')
soup.prettify()
print(soup.prettify()) #prettify()会为每一个标签添加一个换行符
结果如下:
This is a python demo page
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:
Basic Python
and
Advanced Python
.
总结:
BeautifulSoup
① 理解Bs4库的基本元素
② 了解遍历的方法