安装

如果安装了anaconda的集成库，则不需要再次安装
如果没有，则使用pip指令安装
pip install beautifulsoup4 -i https://pypi.tuna.tsinghua.edu.cn/simple/

查看源代码

方法一：

右键网页，查看源点

方法二：

使用requests库

import requests
from bs4 import BeautifulSoup
kv = {
   'user-agent' : 'Mozilla/5.0'}
url = "https://blog.csdn.net/qq_43321732"
try:
    r = requests.get(url, headers = kv)
    r.raise_for_status()
    demo = r.text
except:
    print("爬取失败")
soup = BeautifulSoup(demo, "html.parser")
print(soup.prettify())

使用Beautiful Soup库

Beautiful Soup库的基本元素

打印标签

import requests
from bs4 import BeautifulSoup
kv = {
   'user-agent' : 'Mozilla/5.0'}
url = "https://ac.nowcoder.com/acm/contest/5666"
try:
    r = requests.get(url)
    r.raise_for_status()
    r.encoding = r.apparent_encoding
    demo = r.text
except:
    print("爬取失败")
soup = BeautifulSoup(demo, "html.parser")
print(soup.title)

打印a标签

import requests
from bs4 import BeautifulSoup
kv = {
   'user-agent' : 'Mozilla/5.0'}
url = "https://ac.nowcoder.com/acm/contest/5666"
try:
    r = requests.get(url)
    r.raise_for_status()
    r.encoding = r.apparent_encoding
    demo = r.text
except:
    print("爬取失败")
soup = BeautifulSoup(demo, "html.parser")
tag = soup.a
print(tag)

a标签属性操作

import requests
from bs4 import BeautifulSoup
kv = {
   'user-agent' : 'Mozilla/5.0'}
url = "https://ac.nowcoder.com/acm/contest/5666"
try:
    r = requests.get(url)
    r.raise_for_status()
    r.encoding = r.apparent_encoding
    demo = r.text
except:
    print("爬取失败")
soup = BeautifulSoup(demo, "html.parser")
tag = soup.a
print(tag.attrs)
print(tag.attrs['class'])
#链接属性
print(tag.attrs['href'])
#标签属性类型(字典类型)
print(type(tag.attrs))
print(type(tag))

html的基本格式

遍历方式

下行遍历

import requests
from bs4 import BeautifulSoup
kv = {
   'user-agent' : 'Mozilla/5.0'}
url = "https://ac.nowcoder.com/acm/contest/5666"
try:
    r = requests.get(url)
    r.raise_for_status()
    r.encoding = r.apparent_encoding
    demo = r.text
except:
    print("爬取失败")
soup = BeautifulSoup(demo, "html.parser")
print(soup.head)
print(soup.head.contents)
print(soup.body.contents)
print(len(soup.head.contents))
print(soup.head.contents[1])

上行遍历

平行遍历

平行遍历必须发生在同一个父亲节点下

更友好的显示html

prettify方法