Uses ReadDirectoryChangesW asynchronously (overlapped mode) to monitor a directory (and its' children) for changes.

monitor-dir.py

import os
import time

import win32file
import win32con
import pywintypes
import winerror

WATCHED_DIR = "./mon"

FILE_ACTIONS = {
  1 : "created",
  2 : "deleted",
  3 : "updated",
  4 : "renamed from",
  5 : "renamed to"
}

def main():
    ol = pywintypes.OVERLAPPED()
    buf = win32file.AllocateReadBuffer(1024)

    # get directory handle
    hDir = win32file.CreateFile (
        WATCHED_DIR,                            # fileName
        0x0001, # FILE_LIST_DIRECTORY           # desiredAccess
        win32con.FILE_SHARE_READ |              # shareMode
        win32con.FILE_SHARE_WRITE | 
        win32con.FILE_SHARE_DELETE,
        None,                                   # attributes
        win32con.OPEN_EXISTING,                 # CreationDisposition
        win32con.FILE_FLAG_BACKUP_SEMANTICS |   # flagsAndAttributes
        win32con.FILE_FLAG_OVERLAPPED, # async
        None                                    # hTemplateFile
    )

    while True:
        # read directory changes async
        win32file.ReadDirectoryChangesW(
            hDir,   # handle
            buf,    # buffer
            True,   # bWatchSubtree
            win32con.FILE_NOTIFY_CHANGE_FILE_NAME | # dwNotifyFilter
            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,
            ol      # overlapped
        )

        bytes = None

        # wait for changes
        while bytes == None:
            try:
                bytes = win32file.GetOverlappedResult(
                    hDir,   # hFile
                    ol,     # overlapped
                    False   # bWait
                )

            except pywintypes.error as err:
                if err.winerror == winerror.ERROR_IO_INCOMPLETE:
                    # not available yet, wait for a bit
                    time.sleep(0.1)

                else:
                    # other error...
                    raise err

        # get changes from buffer
        result = win32file.FILE_NOTIFY_INFORMATION(buf, bytes)

        # print results
        for action, filename in result:
            print(FILE_ACTIONS.get(action, "Unknown"), filename)

        print("---")

if __name__ == "__main__":
    main()