Watch File Changes And Do Something

import typing as t
from time import sleep
 
from lk_utils import fs
from watchdog.events import FileModifiedEvent
from watchdog.events import FileSystemEventHandler
from watchdog.observers import Observer
 
 
def on_file_change(filepath: str, callback: t.Callable) -> None:
    observer = Observer()
    handler = FileEventHandler(filepath, callback)
    observer.schedule(handler, fs.parent(filepath), recursive=False)
    _polling(observer)
 
 
class FileEventHandler(FileSystemEventHandler):
    def __init__(self, filepath: str, callback: t.Callable) -> None:
        super().__init__()
        self._filepath = fs.normpath(filepath, True)
        self._callback = callback
 
    def on_modified(self, event: FileModifiedEvent) -> None:
        # print(event.src_path)
        if not event.is_directory:
            if event.src_path == self._filepath:
                self._callback()
 
 
def _polling(observer: Observer) -> None:
    print("start polling. you can press `ctrl + c` to stop it.")
    observer.start()
    try:
        while True:
            sleep(1)
    except KeyboardInterrupt:
        observer.stop()
        print("watchdog stopped")
    finally:
        observer.join()