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.title)
tag = soup.a
print(tag)

title>This is a python demo page/title>
a   >Basic Python/a>

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.a.name)
print(soup.a.parent.name)
print(soup.a.parent.parent.name)

a
p   
body

import requests
from bs4 import BeautifulSoup
r = requests.get("http://python123.io/ws/demo.html")
demo = r.text
soup = BeautifulSoup(demo,"html.parser")
tag = soup.a
print(tag.attrs)
print(tag.attrs['class'])
print(tag.attrs['href'])
print(type(tag.attrs))
print(type(tag))

{'href': 'http://www.icourse163.org/course/BIT-268001', 'class': ['py1'], 'id': 'link1'}
['py1']
http://www.icourse163.org/course/BIT-268001
class 'dict'>
class 'bs4.element.Tag'>

import requests
from bs4 import BeautifulSoup
newsoup = BeautifulSoup("b>!--This is a comment-->/b>p>This is not a comment/p>","html.parser")
print(newsoup.b.string)
print(type(newsoup.b.string))
print(newsoup.p.string)
print(type(newsoup.p.string))

This is a comment
class 'bs4.element.Comment'>
This is not a comment
class 'bs4.element.NavigableString'>

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)
print(soup.body.contents)
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>]
['\n', p >b>The demo python introduces several python courses./b>/p>, '\n', p >Python 
is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the 
following courses:
a   >Basic Python/a> and a   >Advanced Python/a>./p>, '\n']
5
p >b>The demo python introduces several python courses./b>/p>

for child in soup.body.children:
	print(child)  #遍歷兒子結點
for child in soup.body.descendants:
	print(child) #遍歷子孫節點

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.title.parent)
print(soup.html.parent)

head>title>This is a python demo page/title>/head>
html>head>title>This is a python demo page/title>/head>
body>
p >b>The demo python introduces several python courses./b>/p>
p >Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
a   >Basic Python/a> and a   >Advanced Python/a>./p>
/body>/html>

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:
        print(parent)
    else:
        print(parent.name)

p
body      
html      
[document]

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.a.next_sibling)
print(soup.a.next_sibling.next_sibling)

print(soup.a.previous_sibling)
print(soup.a.previous_sibling.previous_sibling)

print(soup.a.parent)

and 
a class="py2"  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:

None
p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
a class="py1"  id="link1">Basic Python/a> and a class="py2"  id="link2">Advanced Python/a>./p>

for sibling in soup.a.next_sibling:
	print(sibling)  #遍歷后續節點
for sibling in soup.a.previous_sibling:
	print(sibling)  #遍歷前續節點

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.prettify())

html>
 head>
  title>
   This is a python demo page
  /title>
 /head>
 body>
  p class="title">
   b>
    The demo python introduces several python courses.
   /b>
  /p>
  p class="course">
   Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
    Basic Python
   /a>
   and
   a class="py2"  id="link2">
    Advanced Python
   /a>
   .
  /p>
 /body>
/html>

import requests
from bs4 import BeautifulSoup

soup = BeautifulSoup("p>中文/p>","html.parser")
print(soup.p.string)

print(soup.p.prettify())

中文

p>  
 中文
/p>