filtercss

filtercss lets you filter unused rules from CSS files, like https://purgecss.com/ but in Python.

Installation

pip install filtercss

Example

Filtering is simple, just use filter_css.

from filtercss import filter_css

css = """
.test1, .test3 {
    color: red;
}
.test2 {
    color: blue;
}
"""

html = """
<a class="test1 some-other-cls">test</a>
"""

res_css = filter_css(css, html)
assert "test1" in res_css
assert "test2" not in res_css

Limitations

filtercss uses tinycss2. Also filtercss will not be able to anticipate what DOM elements might be inserted by any JavaScript and thus will happily filter out the unused CSS rules they might want to use. filtercss uses BeautifulSoup4 to parse HTML and to detect whether a CSS selector in a rule matches against a given file. However, BeautifulSoup4 might not support all of the CSS selectors, in which case filtercss is conservative and includes the given CSS rule. filtercss is also not optimal in that it includes a full CSS rule if any of its selectors matches and it does not filter out unmatched selectors from the rule. Note that this may change in the future.

License

MIT License