BeautifulSoup庫的安裝與使用

時間 2019-11-17

標籤 beautifulsoup 安裝使用简体版

原文原文鏈接

BeautifulSoup庫的安裝

Win平臺：「以管理員身份運行」 cmdhtml

執行 pip install beautifulsoup4python

演示HTML頁面地址：http://python123.io/ws//demo.html

文件名稱：demo.htmlui

網頁源代碼：HTML 5.0 格式代碼編碼

BeautifulSoup庫的安裝小測：

>>> import requests
>>> r = requests.get("http://python123.io/ws//demo.html")
>>> r.text
'<html><head><title>This is a python demo page</title></head>\r\n<body>\r\n<p class="title"><b>The demo python introduces several python courses.</b></p>\r\n<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\r\n<a href="http://www.icourse163.org/course/BIT-268001" class="py1" id="link1">Basic Python</a> and <a href="http://www.icourse163.org/course/BIT-1001870001" class="py2" id="link2">Advanced Python</a>.</p>\r\n</body></html>'
>>> demo = r.text
>>> from bs4 import BeautifulSoup
>>> 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:
   <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">
    Basic Python
   </a>
   and
   <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">
    Advanced Python
   </a>
   .
  </p>
 </body>
</html>
>>>

Beautiful Soup庫的基本元素：

Beautiful Soup庫的理解：spa

Beautiful Soup庫是解析、遍歷、維護「標籤樹」的功能庫。3d

<p>..</p> : 標籤Tagcode

Beautiful Soup庫的引用：

　　 from bs4 import BeautifulSouphtm

　　 import bs4blog

Beautiful Soup庫解析器：ip

soup = BeautifulSoup ('<html>data</html>','html.parser')

BeautifulSoup類的基本元素：

< p class = "title" > ... </p>

Tag標籤：

>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo,'html.parser')
>>> soup.title
<title>This is a python demo page</title>
>>> tag = soup.a
>>> tag
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>

任何存在於HTML語法中的標籤均可以用soup.<tag>訪問得到當HTML文檔中存在多個相同<tag>對應內容時，soup.<tag>返回第一個

Tag的name:

>>> from bs4 import BeautifulSoup
>>> soup = BeautifulSoup(demo,'html.parser')
>>> soup.a.name
'a'
>>> soup.a.parent.name
'p'
>>> soup.a.parent.parent.name
'body'
>>>

每一個<tag>都有本身的名字，經過<tag>.name獲取，字符串類型

Tag的attrs(屬性)：

>>> tag = soup.a
>>> tag.attrs
{'href': 'http://www.icourse163.org/course/BIT-268001', 'class': ['py1'], 'id': 'link1'}
>>> tag.attrs['class']
['py1']
>>> tag.attrs['href']
'http://www.icourse163.org/course/BIT-268001'
>>> type(tag.attrs)
<class 'dict'>
>>> type(tag)
<class 'bs4.element.Tag'>

一個<tag>能夠有0或多個屬性，字典類型

Tag的NavigableString:

>>> soup.a
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a>
>>> soup.a.string
'Basic Python'
>>> soup.p
<p class="title"><b>The demo python introduces several python courses.</b></p>
>>> soup.p.string
'The demo python introduces several python courses.'
>>> type(soup.p.string)
<class 'bs4.element.NavigableString'>

NavigableString能夠跨越多個層次

Tag的Comment：

>>> newsoup = BeautifulSoup("<b><!--This is a comment--></b><p>This is not a comment</p>","html.parser")
>>> newsoup.b.string
'This is a comment'
>>> type(newsoup.b.string)
<class 'bs4.element.Comment'>
>>> newsoup.p.string
'This is not a comment'
>>> type(newsoup.p.string)
<class 'bs4.element.NavigableString'>

Comment是一種特殊類型

標籤<tag>

基於bs4庫的HTML內容遍歷方法：

HTML基本格式：

<>...</>構成了所屬關係，造成了標籤的樹形結構

標籤樹的下行遍歷：

BeautifulSoup類型是標籤樹的根節點

標籤樹的下行遍歷

>>> soup = BeautifulSoup(demo,'html.parser')
>>> soup.head
<head><title>This is a python demo page</title></head>
>>> soup.head.contents
[<title>This is a python demo page</title>]
>>> soup.body.contents
['\n', <p class="title"><b>The demo python introduces several python courses.</b></p>, '\n', <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" href="http://www.icourse163.org/course/BIT-268001" id="link1">Basic Python</a> and <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">Advanced Python</a>.</p>, '\n']
>>> len(soup.body.contents)
5
>>> soup.body.contents[1]
<p class="title"><b>The demo python introduces several python courses.</b></p>

遍歷兒子節點：

for child in soup.body.children:
    print(child)

遍歷子孫節點：

for child in soup.body.descendants:
    print(child)

標籤樹的上行遍歷：

soup = BeautifulSoup(demo,'html.parser')
for parent in soup.a.parents:           #標籤樹的上行遍歷
    if parent is None:
        print(parent)
    else:
        print(parent.name)

遍歷全部先輩節點，包括soup自己，因此要區別判斷

運行結果：

標籤樹的平行遍歷：

平行遍歷發生在同一個父節點下的各節點間

遍歷的判斷：

讓HTML內容更加「友好」的顯示：

bs4庫的prettify()方法：

>>> import requests
>>> r = requests.get("http://python123.io/ws//demo.html")
>>> demo = r.text
>>> demo
'<html><head><title>This is a python demo page</title></head>\r\n<body>\r\n<p class="title"><b>The demo python introduces several python courses.</b></p>\r\n<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\r\n<a href="http://www.icourse163.org/course/BIT-268001" class="py1" id="link1">Basic Python</a> and <a href="http://www.icourse163.org/course/BIT-1001870001" class="py2" id="link2">Advanced Python</a>.</p>\r\n</body></html>'
>>> soup = BeautifulSoup(demo,'html.parser')
>>> soup.prettify()
'<html>\n <head>\n  <title>\n   This is a python demo page\n  </title>\n </head>\n <body>\n  <p class="title">\n   <b>\n    The demo python introduces several python courses.\n   </b>\n  </p>\n  <p class="course">\n   Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:\n   <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">\n    Basic Python\n   </a>\n   and\n   <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">\n    Advanced Python\n   </a>\n   .\n  </p>\n </body>\n</html>'
>>> 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:
   <a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">
    Basic Python
   </a>
   and
   <a class="py2" href="http://www.icourse163.org/course/BIT-1001870001" id="link2">
    Advanced Python
   </a>
   .
  </p>
 </body>
</html>

.prettify()爲HTML文本<>及其內容增長'\n'

.prettify()可用於標籤，方法：<tag>.prettify()

>>> print(soup.a.prettify())
<a class="py1" href="http://www.icourse163.org/course/BIT-268001" id="link1">
 Basic Python
</a>

bs4庫的編碼：

bs4庫將任何HTML輸入都變爲utf-8編碼，Python 3.x默認支持編碼是utf-8，解析無障礙。

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

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