遍历文档树

1.直接子节点：.contents .children属性

.content

Tag的.content属性可以将Tag的子节点以列表的方式输出

#!/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>
 
# 创建 Beautiful Soup 对象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
 
# 输出方式为列表
print(soup.head.contents)
 
print(soup.head.contents[0])

运行结果

[<title>The Dormouse's story</title>]
<title>The Dormouse's story</title>

.children

它返回的不是一个列表，不过我们可以通过遍历获取所有的子节点。

#!/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>
"""
 
# 创建 Beautiful Soup 对象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
 
# 输出方式为列表生成器对象
print(soup.head.children)
 
# 通过遍历获取所有子节点
for child in soup.head.children:
    print(child)

运行结果

<list_iterator object at 0x008FF950>
<title>The Dormouse's story</title>

相关推荐：《Python相关教程》

2.所有子孙节点：.descendants属性

上面讲的.contents和.children属性仅包含Tag的直接子节点，.descendants属性可以对所有Tag的子孙节点进行递归循环，和children类似，我们也需要通过遍历的方式获取其中的内容。

#!/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>
"""
 
# 创建 Beautiful Soup 对象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
 
# 输出方式为列表生成器对象
print(soup.head.descendants)
 
# 通过遍历获取所有子孙节点
for child in soup.head.descendants:
    print(child)

运行结果

<generator object descendants at 0x00519AB0>
<title>The Dormouse's story</title>
The Dormouse's story

3.节点内容：.string属性

如果Tag只有一个NavigableString类型子节点，那么这个Tag可以使用.string得到子节点。如果一个Tag仅有一个子节点，那么这个Tab也可以使用.string方法，输出结果与当前唯一子节点的.string结果相同。

通俗点来讲就是：如果一个标签里面没有标签了，那么.string就会返回标签里面的内容。如果标签里面只有唯一的一个标签了，那么.string也会返回里面的内容。例如：

#!/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>
"""
 
# 创建 Beautiful Soup 对象，指定lxml解析器
soup = BeautifulSoup(html, "lxml")
 
print(soup.head.string)
 
print(soup.head.title.string)

运行结果

The Dormouse's story
The Dormouse's story

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