python如何遍历文档树？这样的python用法别说你不会

1、python如何遍历文档树——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 = """

The Dormouse's story

Once upon a time there were three little sisters; and their names were

,

Lacie and

Tillie;

and they lived at the bottom of a well.

...

"""

# 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

[]

.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 = """

The Dormouse's story

Once upon a time there were three little sisters; and their names were

,

Lacie and

Tillie;

and they lived at the bottom of a well.

...

"""

# 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

2、python如何遍历文档树——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 = """

The Dormouse's story

Once upon a time there were three little sisters; and their names were

,

Lacie and

Tillie;

and they lived at the bottom of a well.

...

"""

# 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

The Dormouse's story

3、python如何遍历文档树——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 = """

The Dormouse's story

Once upon a time there were three little sisters; and their names were

,

Lacie and

Tillie;

and they lived at the bottom of a well.

...

"""

# 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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