ReadDirectoryChangesW

""" Watched Folder or Hot Folder.
Observes a folder for file changes, e.g. new/edited/deleted files.

inspired by: http://timgolden.me.uk/python/win32_how_do_i/watch_directory_for_changes.html
"""

import os
import threading

import win32file
import win32con

# actions
ACTIONS = {
  1 : "Created",
  2 : "Deleted",
  3 : "Updated",
  4 : "Renamed from something",
  5 : "Renamed to something"
}

# constants
FILE_LIST_DIRECTORY = 0x0001

class WatchedFolder:
    def __init__(self, path):
        self.path = path
        """ path to watch """
        self.buffer = 1024
        """ buffer size for results """
        self.thread = None
        """ main thread """
        self.stopped = None
        """ set to True to stop watching """
        self.subDirs = True
        """ set to True to watch sub dirs """
        self.filter = win32con.FILE_NOTIFY_CHANGE_FILE_NAME |
            win32con.FILE_NOTIFY_CHANGE_DIR_NAME |
            win32con.FILE_NOTIFY_CHANGE_ATTRIBUTES |
            win32con.FILE_NOTIFY_CHANGE_SIZE |
            win32con.FILE_NOTIFY_CHANGE_LAST_WRITE |
            win32con.FILE_NOTIFY_CHANGE_SECURITY
        """ event filter """
        # directory handle
        self.handle = win32file.CreateFile(
            path,
            FILE_LIST_DIRECTORY,
            win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE | win32con.FILE_SHARE_DELETE,
            None,
            win32con.OPEN_EXISTING,
            win32con.FILE_FLAG_BACKUP_SEMANTICS,
            None
        )

    # run loop
    def run(self):
        while not self.stopped:
            results = win32file.ReadDirectoryChangesW(
                self.handle,
                self.buffer,
                self.subDirs,
                self.filter,
                None,
                None
            )
            self.do(results)

    # start watching
    def start(self):
        self.stopped = False
        thread = threading.Thread(target=self.run)
        thread.daemon = True
        thread.start()
        self.thread = thread

    # stop watching
    def stop(self):
        self.stopped = True

    # overwrite this
    def do(self, results):
        for action, item in results:
            fullFilename = os.path.join(self.path, item)
            print fullFilename, ACTIONS.get(action, "Unknown")

def demo():
    import time
    path = os.path.abspath("watch")
    wf = WatchedFolder(path)
    wf.start()
    wait = 10 # wait x seconds
    print "now wait %d seconds..." % wait
    time.sleep(wait)
    print "stop!"
    wf.stop()
    print "stopped"
    # hint: after stopping, the last initiated run still is alive

if __name__ == "__main__":
    demo()