automatic sass to css compiling

auto_sass.py

#!/usr/bin/env python
# auto_sass.py - watches your sass files in a directory and compiles them to a css file
# whenever you save it.
# currently this only works under linux and requires pynotify
# use: ./auto_sass.py <directory>
import os, sys, subprocess
from pyinotify import WatchManager, Notifier, ProcessEvent, IN_CLOSE_WRITE

SASS_FILE_EXTENSION = 'sass'
CSS_FILE_EXTENSION = 'css'


def which(program):
    import os
    def is_exe(fpath):
        return os.path.exists(fpath) and os.access(fpath, os.X_OK)

    fpath, fname = os.path.split(program)
    if fpath:
        if is_exe(program):
            return program
    else:
        for path in os.environ["PATH"].split(os.pathsep):
            exe_file = os.path.join(path, program)
            if is_exe(exe_file):
                return exe_file

    return None


class SassModifyDetector(ProcessEvent):
    
    def __init__(self):
        self.last = None

    def process_IN_CLOSE_WRITE(self, event):
        if event.name and event.path:
            sass_file = os.path.join(event.path, event.name)
            basename, extension = os.path.splitext(sass_file)

            if extension == '.' + SASS_FILE_EXTENSION:
                print "[converting]", sass_file
                css_file = basename + '.' + CSS_FILE_EXTENSION
                p = subprocess.Popen( ('sass %s > %s' % (sass_file, css_file)), stdout=subprocess.PIPE, shell=True)


if __name__ == '__main__':
    try:
        path = sys.argv[1]
    except IndexError:
        print 'Usage: %s directory to monitor' % sys.argv[0]
    else:
        if not which('sass'):
            print 'You need to install sass and/or add it to your path!'
        else:
            wm = WatchManager()
            notifier = Notifier(wm, SassModifyDetector(), 0, 0, 1000)
            wm.add_watch(path, IN_CLOSE_WRITE, rec=True)

            try:
                while 1:
                    notifier.process_events()
                    if notifier.check_events():
                        notifier.read_events()
            except KeyboardInterrupt:
                notifier.stop()