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Python爬蟲如何使用CSS選擇器？針對這個問題，這篇文章詳細介紹了相對應的分析和解答，希望可以幫助更多想解決這個問題的小伙伴找到更簡單易行的方法。
CSS選擇器
這是另一種與find_all()方法有異曲同工的查找方法，寫CSS時，標簽名不加任何修飾，類名前加.，id名前加#。
在這里我們也可以利用類似的方法來篩選元素，用到的方法是soup.select()，返回的類型是list。
（1）通過標簽名查找
#!/usr/bin/python3
# -*- coding:utf-8 -*-
from bs4 import BeautifulSoup
html = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
<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>,
<a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
# 創建 Beautiful Soup 對象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
print(soup.select("title"))
print(soup.select("b"))
print(soup.select("a"))運行結果
[<title>The Dormouse's story</title>] [<b>The Dormouse's story</b>] [<a class="sister" href="http://example.com/elsie" id="link1"><!-- Elsie --></a>, <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>, <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]
（2）通過類名查找
#!/usr/bin/python3
# -*- coding:utf-8 -*-
from bs4 import BeautifulSoup
html = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
<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>,
<a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
# 創建 Beautiful Soup 對象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
print(soup.select(".title"))運行結果
[<p class="title" name="dromouse"><b>The Dormouse's story</b></p>]
（3）通過id名查找
#!/usr/bin/python3
# -*- coding:utf-8 -*-
from bs4 import BeautifulSoup
html = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
<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>,
<a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
# 創建 Beautiful Soup 對象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
print(soup.select("#link1"))運行結果
[<p class="title" name="dromouse"><b>The Dormouse's story</b></p>]
（4）組合查找
#!/usr/bin/python3
# -*- coding:utf-8 -*-
from bs4 import BeautifulSoup
html = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
<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>,
<a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
# 創建 Beautiful Soup 對象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
print(soup.select("p #link1"))運行結果
[<a class="sister" href="http://example.com/elsie" id="link1"><!-- Elsie --></a>]
（5）屬性查找
查找時還可以加入屬性元素，屬性需要用中括號括起來，注意屬性和標簽屬于同一節點，所以中間不能加空格，否則會無法匹配到。
#!/usr/bin/python3
# -*- coding:utf-8 -*-
from bs4 import BeautifulSoup
html = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
<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>,
<a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
# 創建 Beautiful Soup 對象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
print(soup.select("a[class='sister']"))運行結果
[<a class="sister" href="http://example.com/elsie" id="link1"><!-- Elsie --></a>, <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>, <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]
同樣，屬性仍然可以與上述查找方式組合，不在同一節點的空格隔開，同一節點的不加空格。
#!/usr/bin/python3
# -*- coding:utf-8 -*-
from bs4 import BeautifulSoup
html = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
<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>,
<a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
# 創建 Beautiful Soup 對象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
print(soup.select("p a[class='sister']"))運行結果
[<a class="sister" href="http://example.com/elsie" id="link1"><!-- Elsie --></a>, <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>, <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]
（6）獲取內容
以上的select()方法返回的結果都是列表形式，可以遍歷形式輸出，然后用get_text()方法來獲取它的內容。
#!/usr/bin/python3
# -*- coding:utf-8 -*-
from bs4 import BeautifulSoup
html = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title" name="dromouse"><b>The Dormouse's story</b></p>
<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>,
<a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
# 創建 Beautiful Soup 對象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
print(soup.select("p a[class='sister']"))
for item in soup.select("p a[class='sister']"):
print(item.get_text())運行結果
[<a class="sister" href="http://example.com/elsie" id="link1"><!-- Elsie --></a>, <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>, <a class="sister" href="http://example.com/tillie" id="link3"> Tillie</a>] Lacie Tillie
注意：<!-- Elsie -->為注釋內容，未輸出
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