lcss

LCSS

CSS pre-processor written in Python with limited set of features. It's simple and fast.
The key point is to use as much of native CSS as possible and create as less complexity overhead as possible without compromising productivity.

Concept

CSS already supports variables, imports and nesting. What CSS really missing is mixins and bundling - these are provided by LCSS.
LCSS also provides SCSS-like nesting in case if native nesting doesn't meet your needs.

Variables

Native CSS variables - https://developer.mozilla.org/en-US/docs/Web/CSS/Using_CSS_custom_properties .

:root {
  --font-mod: 10px;
  --font-size-main: calc(var(--font-mod) + 6px); /* 16px */
}
details {
  font-size: var(--font-size-main);
}

Modules

Native CSS imports - https://developer.mozilla.org/en-US/docs/Web/CSS/@import .

mybtn.lcss:

.mybtn {
  cursor: pointer;
}

main.lcss:

@import 'mybtn';

body {
  font-size: 16px;
}

Nesting

CSS supports nesting - https://developer.mozilla.org/en-US/docs/Web/CSS/Nesting_selector . However it's not 100% equals to SCSS-like nesting we are used to.

Native nesting example:

.parent {
  font-size: 22px;
  a {
    font-size: 16px;
    &:hover {
      font-weight: 900;
    }
  }
}

This code is equals to:

.parent {
  font-size: 22px;
}
.parent a {
  font-size: 16px;
}
.parent a:hover {
  font-weight: 900;
}

Non-native nesting example:

style.lcss:

.parent {
  &__inner {
    font-size: 22px;
    &:hover {
      font-weight: 900;
    }
  }
}

This will be transpiled to:

.parent__inner {
  font-size: 22px;
}
.parent__inner:hover {
  font-weight: 900;
}

The main difference is that with native nesting you're not able to use & to concatenate selectors as strings.

You can choose preferred nesting method with NATIVE_NESTING (True/False) config parameter.

Mixins

Mixins in LCSS are simple python functions.

mixins.py:

def bg(path):
    return f'''\
    background-image: url({path});
    background-position: center;
    background-repeat: no-repeat;
    background-size: contain;'''

style.lcss:

.box {
  .card {
    padding: 10px;
    @mixin bg('bg.webp');
  }
}

The result will be the following::

.box .card {
  padding: 10px;
  background-image: url(bg.webp);
  background-position: center;
  background-repeat: no-repeat;
  background-size: contain;
}

To make mixins file available, import it in lcss_config.py (see config example below).

Bundling

LCSS automatically replaces all imports with the content.

Installation

pip install lcss

Command line usage

You can use lcss without config file:

lcss style.lcss > style.css
lcss style.lcss mixins_dir > style.css

mixins_dir - directory containing mixins.py file.\

Configuration

To use lcss with config file you should create lcss_config.py (default one is created automatically by calling lcss) in current working directory and then call lcss without arguments.

Example lcss_config.py:

import os
# Mixins in lcss are just a python functions.
# Store mixins in mixins.py file and import it here:
import mixins

BASE_DIR = os.path.dirname(os.path.abspath(__file__))

# Specify source and output files.
FILES = [
    {
        'in': os.path.join(BASE_DIR, 'style.lcss'),
        'out': os.path.join(BASE_DIR, 'style.css'),
    },
]
# If native nesting is disabled, SCSS-like one will be used instead.
NATIVE_NESTING = False

More examples

You can find some examples in tests directory - https://github.com/SergeiMinaev/lcss/tree/dev/tests:

pip install lcss
git clone [e-mail]:SergeiMinaev/lcss.git
cd lcss
lcss tests/nesting_1.lcss
lcss tests/mixins_1.lcss ./tests