FileSystem Directory Watcher

fswatcher.py

# fswatcher.py
# Watches a particular directory for files with corresponding .lock files
#

from twisted.internet import reactor
import os

class DirectoryWatcher(object):
    def __init__(self, dirname, interval=1.0):
        self.dirname = dirname
        self.interval = interval
        self.callbacks = []
        self.known_files = {}
        self._notified = {}

        if not os.path.exists(self.dirname):
            raise Exception, "The watch directory does not exist: %s" % self.dirname

    def start(self):
        self.call = reactor.callWhenRunning(self._checkDir)

    def stop(self):
        self.call.cancel()

    def addCallback(self, cb):
        self.callbacks.append(cb)

    def removeCallback(self, cb):
        self.callbacks.remove(cb)

    def _checkDir(self):
        files=[]
        for dirname, dirnames, filenames in os.walk(self.dirname):
            for fn in filenames:
                files.append(os.path.join(dirname, fn));

        # we have all the files, lets filter .lock files out
        clean_files = [f for f in files if os.path.splitext(f.lower())[1] != '.lock'];
        lock_files = [os.path.basename(f) for f in files if os.path.splitext(f.lower())[1] == '.lock'];

        clean_files_dict = {}
        for c in clean_files:
            id = os.path.splitext(os.path.basename(c))[0]
            if id in clean_files_dict:
                clean_files_dict[id].append(c)
            else:
                clean_files_dict[id] = [c]

        to_notify = []

        for k, v in clean_files_dict.items():
            if k not in self._notified and ('%s.lock' % k) not in lock_files:
                to_notify.append(v)
                self._notified[k] = v

        files_no_more = set(self._notified) - set(clean_files_dict)
        for f in files_no_more:
            del self._notified[f]

        for v in to_notify:
            for cb in self.callbacks:
                cb(v)

        self.call = reactor.callLater(self.interval, self._checkDir)

if __name__ == '__main__':
    def on_file(v):
        print 'Got:', v

    d = DirectoryWatcher('/tmp/watcher-test', 1.0)
    d.addCallback(on_file)
    d.start()

    reactor.run()