python網(wǎng)絡(luò)爬蟲精解之Beautiful Soup的使用說(shuō)明
一、Beautiful Soup的介紹
Beautiful Soup是一個(gè)強(qiáng)大的解析工具，它借助網(wǎng)頁(yè)結(jié)構(gòu)和屬性等特性來(lái)解析網(wǎng)頁(yè)。
它提供一些函數(shù)來(lái)處理導(dǎo)航、搜索、修改分析樹等功能，Beautiful Soup不需要考慮文檔的編碼格式。Beautiful Soup在解析時(shí)實(shí)際上需要依賴解析器，常用的解析器是lxml。
二、Beautiful Soup的使用
test03.html測(cè)試實(shí)例：
<!DOCTYPE html>
<html>
<head>
<meta content="text/html;charset=utf-8" http-equiv="content-type" />
<meta content="IE=Edge" http-equiv="X-UA-Compatible" />
<meta content="always" name="referrer" />
<link rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="stylesheet" type="text/css" />
<title>百度一下，你就知道 </title>
</head>
<body link="#0000cc">
<div id="wrapper">
<div id="head">
<div class="head_wrapper">
<div id="u1">
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trnews">新聞 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trhao123">hao123 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trmap">地圖 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trvideo">視頻 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trtieba">貼吧 </a>
<a class="bri" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_briicon" style="display: block;">更多產(chǎn)品 </a>
</div>
</div>
</div>
</div>
</body>
</html>
1、節(jié)點(diǎn)選擇器
我們之前了解到，一個(gè)網(wǎng)頁(yè)是由若干個(gè)元素節(jié)點(diǎn)組成的，通過(guò)提取某個(gè)節(jié)點(diǎn)的具體內(nèi)容，就可以獲取到界面呈現(xiàn)的一些數(shù)據(jù)。使用節(jié)點(diǎn)選擇器能夠簡(jiǎn)化我們獲取數(shù)據(jù)的過(guò)程，在不使用正則表達(dá)式的前提下，精準(zhǔn)的獲取數(shù)據(jù)。
from bs4 import BeautifulSoup
file = open("./test03.html",'rb')
html = file.read()
soup = BeautifulSoup(html,'lxml')
print(soup.head)
print(soup.head.title)
print(soup.a)
【運(yùn)行結(jié)果】
<head>
<meta content="text/html;charset=utf-8" http-equiv="content-type"/>
<meta content="IE=Edge" http-equiv="X-UA-Compatible"/>
<meta content="always" name="referrer"/>
<link rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="stylesheet" type="text/css"/>
<title>百度一下，你就知道 </title>
</head>
<title>百度一下，你就知道 </title>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trnews">新聞 </a>
分析：
第一條打印數(shù)據(jù)為獲取網(wǎng)頁(yè)的head節(jié)點(diǎn)；
第二條打印內(nèi)容是獲取head節(jié)點(diǎn)中title節(jié)點(diǎn)，獲取該節(jié)點(diǎn)使用了一個(gè)嵌套選擇，因?yàn)閠itle節(jié)點(diǎn)是嵌套在head節(jié)點(diǎn)里面的；
第三條打印內(nèi)容是獲取a節(jié)點(diǎn)，在源碼中我們看到有許多條a節(jié)點(diǎn)，而只匹配到第一個(gè)a節(jié)點(diǎn)就結(jié)束了。當(dāng)有多個(gè)節(jié)點(diǎn)時(shí)，這種選擇方式指只會(huì)選擇第一個(gè)匹配的節(jié)點(diǎn)，其他后面節(jié)點(diǎn)會(huì)忽略。
2、提取信息
一般我們需要的數(shù)據(jù)位于節(jié)點(diǎn)名、屬性值、文本值中，以下代碼展示了如何獲取這三個(gè)地方的數(shù)據(jù)：
from bs4 import BeautifulSoup
file = open("./test03.html",'rb')
html = file.read()
soup = BeautifulSoup(html,'lxml')
print(soup.body.name)
print(soup.body.a.attrs['class'])
print(soup.body.a.attrs['href'])
print(soup.body.a.string)
【運(yùn)行結(jié)果】
body
['mnav']
http://news.baidu.com
新聞
分析：
第一條獲取body節(jié)點(diǎn)名；
第二條獲取a節(jié)點(diǎn)class屬性值；
第三條獲取a節(jié)點(diǎn)href屬性值；
第四條獲取a節(jié)點(diǎn)的文本值；
3、關(guān)聯(lián)選擇
（1）子節(jié)點(diǎn)和子孫節(jié)點(diǎn)
子節(jié)點(diǎn)可以調(diào)用contents屬性和children屬性，子孫節(jié)點(diǎn)可以調(diào)用descendants屬性，他們返回結(jié)果都是生成器類型，通過(guò)for循環(huán)輸出匹配到的信息。
from bs4 import BeautifulSoup
file = open("./test03.html",'rb')
html = file.read()
soup = BeautifulSoup(html,'lxml')
# print(soup.body.contents)
for i,content in enumerate(soup.body.contents):
print(i,content)
【運(yùn)行結(jié)果】
0
1 <div id="wrapper">
<div id="head">
<div class="head_wrapper">
<div id="u1">
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trnews">新聞 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trhao123">hao123 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trmap">地圖 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trvideo">視頻 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trtieba">貼吧 </a>
<a class="bri" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_briicon" style="display: block;">更多產(chǎn)品 </a>
</div>
</div>
</div>
</div>
2
（2）父節(jié)點(diǎn)和祖先節(jié)點(diǎn)
獲取某個(gè)節(jié)點(diǎn)的父節(jié)點(diǎn)可以調(diào)用parent屬性，例如獲取實(shí)例中title節(jié)點(diǎn)的父節(jié)點(diǎn)：
file = open("./test03.html",'rb')
html = file.read()
soup = BeautifulSoup(html,'lxml')
print(soup.title.parent)
【運(yùn)行結(jié)果】
<head>
<meta content="text/html;charset=utf-8" http-equiv="content-type"/>
<meta content="IE=Edge" http-equiv="X-UA-Compatible"/>
<meta content="always" name="referrer"/>
<link rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="stylesheet" type="text/css"/>
<title>百度一下，你就知道 </title>
</head>
同理，如果是想要獲取節(jié)點(diǎn)的祖先節(jié)點(diǎn)，則可調(diào)用parents屬性。
（3）兄弟節(jié)點(diǎn)
調(diào)用next_sibling獲取節(jié)點(diǎn)的下一個(gè)兄弟元素；
調(diào)用previous_sibling獲取節(jié)點(diǎn)的上一個(gè)兄弟元素；
調(diào)用next_siblings取節(jié)點(diǎn)的下一個(gè)兄弟節(jié)點(diǎn)；
調(diào)用previous_siblings獲取節(jié)點(diǎn)的上一個(gè)兄弟節(jié)點(diǎn)；
4、方法選擇器
find_all（）
查找所有符合條件的元素，其使用方法如下：
find_all(name,attrs,recursive,text,**kwargs)
（1）name
根據(jù)節(jié)點(diǎn)名來(lái)查詢?cè)兀绮樵儗?shí)例中a標(biāo)簽元素：
from bs4 import BeautifulSoup
file = open("./test03.html",'rb')
html = file.read()
soup = BeautifulSoup(html,'lxml')
print(soup.find_all(name = "a"))
for a in soup.find_all(name = "a"):
print(a)
【運(yùn)行結(jié)果】
[<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trnews">新聞 </a>, <a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trhao123">hao123 </a>, <a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trmap">地圖 </a>, <a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trvideo">視頻 </a>, <a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trtieba">貼吧 </a>, <a class="bri" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_briicon" style="display: block;">更多產(chǎn)品 </a>]
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trnews">新聞 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trhao123">hao123 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trmap">地圖 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trvideo">視頻 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trtieba">貼吧 </a>
<a class="bri" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_briicon" style="display: block;">更多產(chǎn)品 </a>
（2）attrs
在查詢時(shí)我們還可以傳入標(biāo)簽的屬性，attrs參數(shù)的數(shù)據(jù)類型是字典。
from bs4 import BeautifulSoup
file = open("./test03.html",'rb')
html = file.read()
soup = BeautifulSoup(html,'lxml')
print(soup.find_all(name = "a",attrs = {"class":"bri"}))
【運(yùn)行結(jié)果】
[<a class="bri" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_briicon" style="display: block;">更多產(chǎn)品 </a>]
可以看到，在加上class=“bri”屬性時(shí)，查詢結(jié)果就只剩一條a標(biāo)簽元素。
（3）text
text參數(shù)可以用來(lái)匹配節(jié)點(diǎn)的文本，傳入的可以是字符串，也可以是正則表達(dá)式對(duì)象。
import re
from bs4 import BeautifulSoup
file = open("./test03.html",'rb')
html = file.read()
soup = BeautifulSoup(html,'lxml')
print(soup.find_all(name = "a",text = re.compile('新聞')))
【運(yùn)行結(jié)果】
[<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trnews">新聞 </a>]
只包含文本內(nèi)容為“新聞”的a標(biāo)簽。
find（）
find（）的使用與前者相似，唯一不同的是，find進(jìn)匹配搜索到的第一個(gè)元素，然后返回單個(gè)元素，find_all（）則是匹配所有符合條件的元素，返回一個(gè)列表。
5、CSS選擇器
使用CSS選擇器時(shí)，調(diào)用select（）方法，傳入相應(yīng)的CSS選擇器；
例如使用CSS選擇器獲取實(shí)例中的a標(biāo)簽
from bs4 import BeautifulSoup
file = open("./test03.html",'rb')
html = file.read()
soup = BeautifulSoup(html,'lxml')
print(soup.select('a'))
for a in soup.select('a'):
print(a)
【運(yùn)行結(jié)果】
[<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trnews">新聞 </a>, <a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trhao123">hao123 </a>, <a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trmap">地圖 </a>, <a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trvideo">視頻 </a>, <a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trtieba">貼吧 </a>, <a class="bri" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_briicon" style="display: block;">更多產(chǎn)品 </a>]
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trnews">新聞 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trhao123">hao123 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trmap">地圖 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trvideo">視頻 </a>
<a class="mnav" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_trtieba">貼吧 </a>
<a class="bri" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" name="tj_briicon" style="display: block;">更多產(chǎn)品 </a>
獲取屬性
獲取上述a標(biāo)簽中的href屬性
from bs4 import BeautifulSoup
file = open("./test03.html",'rb')
html = file.read()
soup = BeautifulSoup(html,'lxml')
for a in soup.select('a'):
print(a['href'])
【運(yùn)行結(jié)果】
http://news.baidu.com
https://www.hao123.com
http://map.baidu.com
http://v.baidu.com
http://tieba.baidu.com
//www.baidu.com/more/
獲取文本
獲取上述a標(biāo)簽的文本內(nèi)容，使用get_text()方法，或者是string獲取文本內(nèi)容
from bs4 import BeautifulSoup
file = open("./test03.html",'rb')
html = file.read()
soup = BeautifulSoup(html,'lxml')
for a in soup.select('a'):
print(a.get_text())
print(a.string)
【運(yùn)行結(jié)果】
新聞
新聞
hao123
hao123
地圖
地圖
視頻
視頻
貼吧
貼吧
更多產(chǎn)品
更多產(chǎn)品
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