利用它可以不用編寫正則表達式即可方便的實現網頁信息的提取。

pip3 install beautifulsoup4

用法講解：
常用解析庫：

lxml HTML解析器?

lxml XML解析器

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.prettify())? #格式化代碼

print(soup.title.string)

------------------------------------------------------------------

#標簽選擇器：

##選擇元素：

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.title)

print(type(soup.title))

print(soup.head)

print(soup.p)

如果有很多滿足條件，只會輸出第一個。

##獲取名稱：

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.title.name)

##獲取屬性：

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.p.attrs['name'])#獲取name屬性的值

print(soup.p['name'])

##獲取內容:

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.p.string)

##嵌套選擇：

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.head.title.string)

##1、子節點和子孫節點：

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.p.children)#迭代器

for i,child in enumerate(soup.p.children):

? ? print(i,child)

##2

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.p.contents)#獲取p內的所有內容，列表

##3

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.p.descendants) #迭代器

for i,child in enumerate(soup.p.descendants):

? ? print(i,child)

##1、父節點和祖先節點：

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.p.parent) #迭代器

##2

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(enumerate(list(soup.p.parents))) #迭代器

##兄弟節點

from bst import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(list(enumerate(soup.a.next_siblings)))

print(list(enumerate(soup.a.privious_siblings)))

------------------------------------------------------------------

#標準選擇器

find_all(name,attrs,recursive,text,**kwargs)

可根據標簽名、屬性、內容查找文檔

##name

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'html')

print(soup.find_all(''ul))

print(type(soup.find_all('ul')[0]))

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

for ul in soup.find_all('ul'):

????print(ul.find_all('li'))

##attrs

from bs4? import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.find_all(attrs={'id':'list-1'}))

print(soup.find_all(attrs = {'name':'element'}))

print(soup.find_all(id = 'list-1'))

print(soup.find_all(class_='element')) ##以上四句的輸出一樣

##text

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.find_all(text='Foo'))

#find(name,attrs,recursive,text,**kwargs)

返回單個元素.

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

print(soup.find('ul'))

print(type(soup.find('ul')))

print(soup.find('page'))

#find_parents()，find_parent()

find_next_siblings() find_next_sibling()

find_all_next()? find_next()

find_all_previous() find_previous()

#CSS選擇器??

通過select()直接傳入CSS選擇器即可完成選擇

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

pirnt(soup.select('.panel.panel-heading'))# class用.

print(soup.select('ul li'))

print(soup.select('#list-2.element'))

print(type(soup.select('ul')[0]))#

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

for ul in soup.select('ul'):

? ? print(ul.select('li'))

##獲取屬性

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

for ul in soup.select('ul'):

? ? print(u['id'])

? ? print(ul.attrs['id'])

##獲取內容

from bs4 import BeautifulSoup

soup = BeautifulSoup(html,'lxml')

for ul in soup.select('li'):

? ? print(li.get_text())

#標簽選擇器

#標準選擇器

#CSS選擇器

總結：

?* 推薦使用lxml解析庫,必要使用html.parser

?* 標簽選擇篩選功能弱但是速度快。

?* 建議使用find()，find_all()查詢匹配單個結果或者多個結果。

?* 如果對CSS選擇器熟悉可以使用select()

?* 記住常用的獲取屬性和文本值的方法。

總結

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