Example：
html文件：
html_doc = """ <html><head><title>The Dormouse‘s story</title></head> <p class="title">The Dormouse‘s story
<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 href="http://example.com/lacie" class="sister" id="link2">Lacie and <a href="http://example.com/tillie" class="sister" id="link3">Tillie; and they lived at the bottom of a well.
<p class="story">...
"""
代码：
from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc)
接下来可以开始使用各种功能
soup.X (X为任意标签，返回整个标签，包括标签的属性，内容等）
如：soup.title
# <title>The Dormouse‘s story</title>
soup.p
# <p class="title">The Dormouse‘s story
soup.a （注：仅仅返回第一个结果）
# <a class="sister" href="http://example.com/elsie" id="link1">Elsie
soup.find_all(‘a‘) （find_all 可以返回所有）
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie,
# <a class="sister" href="http://example.com/lacie" id="link2">Lacie,
# <a class="sister" href="http://example.com/tillie" id="link3">Tillie]
find还可以按属性查找
soup.find(id="link3")
# <a class="sister" href="http://example.com/tillie" id="link3">Tillie
要取某个标签的某个属性，可用函数有 find_all,get
for link in soup.find_all(‘a‘):
print(link.get(‘href‘))
# http://example.com/elsie
# http://example.com/lacie
# http://example.com/tillie
要取html文件中的所有文本，可使用get_text()
print(soup.get_text())
# The Dormouse‘s story
#
# The Dormouse‘s story
#
# Once upon a time there were three little sisters; and their names were
# Elsie,
# Lacie and
# Tillie;
# and they lived at the bottom of a well.
#
# ...
如果是打开html文件，语句可用：
soup = BeautifulSoup(open("index.html"))
BeautifulSoup中的Object
tag （对应html中的标签）
tag.attrs (以字典形式返回tag的所有属性）
可以直接对tag的属性进行增、删、改，跟操作字典一样
tag[‘class‘] = ‘verybold‘
tag[‘id‘] = 1
tag
# <blockquote class="verybold" id="1">Extremely bold</blockquote>
del tag[‘class‘]
del tag[‘id‘]
tag
# <blockquote>Extremely bold</blockquote>
tag[‘class‘]
# KeyError: ‘class‘
print(tag.get(‘class‘))
# None
X.contents (X为标签，可返回标签的内容）
eg.
head_tag = soup.head
head_tag
# <head><title>The Dormouse‘s story</title></head>
head_tag.contents
[<title>The Dormouse‘s story</title>]
title_tag = head_tag.contents[0]
title_tag
# <title>The Dormouse‘s story</title>
title_tag.contents
# [u‘The Dormouse‘s story‘]