# 2.2 BeautifulSoup 解析网页: CSS
## CSS 的 Class
CSS 在装饰每一个网页部件的时候, 都会给它一个名字. 而且一个类型的部件, 名字都可以一样
里面的字体/背景颜色, 字体大小, 都是由 CSS 来掌控的, CSS 的代码, 可能就会放在这个网页的 < head> 中
```python
from bs4 import BeautifulSoup
from urllib.request import urlopen
# if has Chinese, apply decode()
html = urlopen("https://morvanzhou.github.io/static/scraping/list.html").read().decode('utf-8')
print(html)
```
```markup
...
...
```
在 < head> 中,被放在 < style> 里面的都是某些 class 的 CSS 代码.，比如 jan 就是一个 class，jan 这个类掌控了这个类型的背景颜色，所以在 < ul class="jan"> 这里, 这个 ul 的背景颜色就是黄色的，而如果是 month 这个类, 它们的字体颜色就是红色
## 按 Class 匹配
找所有 class=month 的信息. 并打印出它们的 tag 内文字.
```python
soup = BeautifulSoup(html, features='lxml')
# use class to narrow search
month = soup.find_all('li', {"class": "month"})
for m in month:
print(m.get_text())
"""
一月
二月
三月
四月
五月
"""
```
找到 class=jan 的信息. 然后在 < ul> 下面继续找 < ul> 内部的< li> 信息
```python
jan = soup.find('ul', {"class": 'jan'})
d_jan = jan.find_all('li') # use jan as a parent
for d in d_jan:
print(d.get_text())
"""
一月一号
一月二号
一月三号
"""
```
---
# Agent Instructions: Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://baozoulin.gitbook.io/python/beautifulsoup-jie-xi-wang-ye/beautifulsoup-jie-xi-wang-98753a-css.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.