CleanCSS

CleanCSS is a simple pythonic language for CSS inspired by CleverCSS but simpler and with less obstrusive features.

Why

I really liked the idea behind CleverCSS but when used in production I realized that I was trying to get away from its parser by escaping strings and unsupported CSS properties way too often. Using vendor prefixes like -webkit-gradient and values such as rgba resulted in a messy CSS, so I decided to write my own parser for a similar syntax without all the complex features that I did not use anyway and it now works fine for me in REAL modern websites.

Syntax examples

I'm going to keep the CleverCSS examples where possible since the syntax is really similar.

A small example below. Note the indentation based syntax and how you can nest rules:

#header, #footer:
    margin: 0
    padding: 0
    font->
        family: Verdana, sans-serif
        size: .9em

    li:
        padding: 0.4em
        margin: 0.8em 0 0.8em

        h3:
            font-size: 1.2em
        p:
            padding: 0.3em
        p.meta:
            text-align: right
            color: #ddd

Of course you can do the very same in CSS, but because of its flat nature the code would look more verbose. The following piece of code is the CleanCSS output of the above file:

#header, #footer {
    margin: 0;
    padding: 0;
    font-family: Verdana, sans-serif
    font-size: .9em
}

#header li,
#footer li {
    padding: 0.4em;
    margin: 0.8em 0 0.8em;
}

#header li h3,
#footer li h3 {
    font-size: 1.2em;
}

#header li p,
#footer li p {
    padding: 0.3em;
}

#header li p.meta,
#footer li p.meta {
    text-align: right;
    color: #dddddd;
}

Callbacks

Starting with version 1.4 CleanCSS supports user callbacks to alter the resulting stylesheet. The callback function receives the property name and its value and should return a list of property-value pairs to insert in the generated CSS.

Example:

import cleancss

def callback(prop, value):
    rules = []

    # Include the unaltered rule
    rules.append( (prop, value) )

    # Include a variant of the rule
    rules.append( ("-moz-"+prop, value) )

    return rules

with open('file.ccss') as f:
    print cleancss.convert(f, callback)

The library already includes a callback function that can be used to convert between the most common browser variants

Example:

import cleancss

with open('file.ccss') as f:
    print cleancss.convert(f, cleancss.callbacks.browser_variants)

Library usage

Import the cleancss module and call the convert() function with a file-like object.

Example:

import cleancss
with open('file.ccss') as f:
    print cleancss.convert(f)

Command line usage

Call the cleancss module without parameters to show the usage instructions. Pass any number of files to cleancss and the script will convert the files to CSS and print the result to the console.

Example:

python -m cleancss file.ccss > result.css

LICENSE

Copyright (c) 2010-2011 Massimiliano Torromeo

CleanCSS is free software released under the terms of the BSD license.

See the LICENSE file provided with the source distribution for full details.

Contacts

• Massimiliano Torromeo <massimiliano.torromeo@gmail.com>