```
## 子节点
一个Tag可能包含多个字符串或其它的Tag,这些都是这个Tag的子节点.Beautiful Soup提供了许多操作和遍历子节点的属性.
### .contents和.children
tag的 `.contents` 属性可以将tag的子节点以列表的方式输出
```python
head_tag = soup.head
head_tag
# The Dormouse's story
head_tag.contents
[The Dormouse's story]
title_tag = head_tag.contents[0]
title_tag
# The Dormouse's story
title_tag.contents
# [u'The Dormouse's story']
```
通过tag的 `.children` 生成器,可以对tag的子节点进行循环:
```python
for child in title_tag.children:
print(child)
# The Dormouse's story
```
string
如果一个tag仅有一个子节点,那么这个tag也可以使用 `.string` 方法。如果tag包含了多个子节点,tag就无法确定 `.string` 方法应该调用哪个子节点的内容, `.string` 的输出结果是 `None`
What's it meaning?
如果tag中包含多个字符串 [[2\]](https://www.crummy.com/software/BeautifulSoup/bs4/doc.zh/#id90) ,可以使用 `.strings` 来循环获取:
```python
for string in soup.strings:
print(repr(string))
# u"The Dormouse's story"
# u'\n\n'
# u"The Dormouse's story"
# u'\n\n'
# u'Once upon a time there were three little sisters; and their names were\n'
# u'Elsie'
# u',\n'
# u'Lacie'
# u' and\n'
# u'Tillie'
# u';\nand they lived at the bottom of a well.'
# u'\n\n'
# u'...'
# u'\n'
```
输出的字符串中可能包含了很多空格或空行,使用 `.stripped_strings` 可以去除多余空白内容:
```python
for string in soup.stripped_strings:
print(repr(string))
```
What's the repr() ?
## 兄弟节点
### .next_sibling 和 .previous_sibling
需要小心，上一个\标签和下一个\标签之间的顿号和换行符;
```html
Once upon a time there were three little sisters; and their names were
Elsie,
Lacie and
Tillie;
and they lived at the bottom of a well.
```
```python
link = soup.a
link
# Elsie
link.next_sibling
# u',\n'
link.next_sibling.next_sibling
# Lacie
```
迭代获取兄弟节点
```python
for sibling in soup.a.next_siblings:
print(repr(sibling))
# u',\n'
# Lacie
# u' and\n'
# Tillie
# u'; and they lived at the bottom of a well.'
# None
for sibling in soup.find(id="link3").previous_siblings:
print(repr(sibling))
# ' and\n'
# Lacie
# u',\n'
# Elsie
# u'Once upon a time there were three little sisters; and their names were\n'
```
### .next_elements 和 .previous_elements
两个tag之间的字符串，也会被认为是elements。
解析器先进入\标签,然后是tag中间的字符串,然后关闭\标签
下面的代码，有助于理解next_siblings和next_elements的区别
```python
from bs4 import BeautifulSoup
html_doc = """
The Dormouse's story
The Dormouse's story
Once upon a time there were three little sisters; and their names were
Elsie,
Lacie and
Tillie;
and they lived at the bottom of a well.
...
"""
soup = BeautifulSoup(html_doc, 'html.parser')
tag_a = soup.a
ans = []
for b in tag_a.next_siblings:
print(type(b))
ans.append(b.get_text())
print(ans)
ans = []
for n_e in tag_a.next_elements:
# print(type(n_e))
print(n_e)
ans.append(n_e.get_text())
print(ans)
```
## find_all
###