# 按CSS搜索按照CSS类名搜索tag的功能非常实用,但标识CSS类名的关键字`class`在Python中是保留字,使用`class`做参数会导致语法错误.从Beautiful Soup的4.1.1版本开始,可以通过`class_`参数搜索有指定CSS类名的tag: ``` soup.find_all("a", class_="sister") # [Elsie, # Lacie, # Tillie] ``` `class_`参数同样接受不同类型的`过滤器`,字符串,正则表达式,方法或`True`: ``` soup.find_all(class_=re.compile("itl")) # [

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] def has_six_characters(css_class): return css_class is not None and len(css_class) == 6 soup.find_all(class_=has_six_characters) # [Elsie, # Lacie, # Tillie] ``` tag的`class`属性是[多值属性](http://beautifulsoup.readthedocs.io/zh_CN/latest/#id15).按照CSS类名搜索tag时,可以分别搜索tag中的每个CSS类名: ``` css_soup = BeautifulSoup('

') css_soup.find_all("p", class_="strikeout") # [

] css_soup.find_all("p", class_="body") # [

] ``` 搜索`class`属性时也可以通过CSS值完全匹配: ``` css_soup.find_all("p", class_="body strikeout") # [

] ``` 完全匹配`class`的值时,如果CSS类名的顺序与实际不符,将搜索不到结果: ``` soup.find_all("a", attrs={"class": "sister"}) # [Elsie, # Lacie, # Tillie] ``` --- # 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://jablack-programs.gitbook.io/python-notes/python-spider/beautifulsoup/sou-suo-wen-dang-shu/find_all/an-css-sou-suo.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.