Very, very simple watchdog-based Python interpreter launcher; watches your script for changes and re-runs it

watchme.py

#!/usr/bin/env python3
##
##  watchme.py - monitor *.py files or a given path and re-run 'python <path>'
##
##  Author:   Kevin Ernst
##  Date:     4 February 2026
##  License:  Apache License Version 2.0
##            (https://github.com/gorakhargosh/watchdog/blob/master/LICENSE)
##  Homepage: https://gist.github.com/ernstki/759383313185aae343bc87b989c44241
##
##  sources:
##  - https://github.com/gorakhargosh/watchdog#example-api-usage
##  - https://github.com/yejianye/watchdog-tricks/blob/master/watchdog_tricks/compiler.py#L32
##
import os, sys, glob, time, subprocess
from functools import wraps

from watchdog.events import FileSystemEvent, FileSystemEventHandler
from watchdog.observers import Observer


def trace_event(func):
    """
    source: https://github.com/yejianye/watchdog-tricks/blob/master/watchdog_tricks/utils.py
    license: see https://github.com/yejianye/watchdog-tricks/pull/1#issuecomment-3850884907
    """
    @wraps(func)
    def _traced_func(self, event):
        if hasattr(event, 'dest_path'):
            print('%s: %s -> %s' % (event.event_type, event.src_path,
                                    event.dest_path), file=sys.stderr)
        else:
            print('%s %s' % (event.event_type, event.src_path),
                  file=sys.stderr)
        return func(self, event)
    return _traced_func


class SavedFileHandler(FileSystemEventHandler):
    def __init__(self, *args, **kwargs):
        self.watchpats = []
        self.watched = []
        if 'watchpats' in kwargs:
            for watch in kwargs.get('watchpats'):
                self.watchpats.append(watch)
            del kwargs['watchpats']
        if not self.watchpats:
            self.watchpats = ["*.py"]

        print("Watching for changes to: {}".format(", ".join(self.watchpats)),
              file=sys.stderr)

        for pat in self.watchpats:  # expand all globs now
            self.watched += glob.glob(pat)
        # and make all paths absolute, but ignore this script itself
        self.watched = set([
            os.path.abspath(p) for p in self.watched
            if os.path.abspath(p) != os.path.abspath(__file__)
        ])

        super().__init__(*args, **kwargs)

    @trace_event
    def on_moved(self, e):  # many/most? editors save with delete, then move
        if os.path.dirname(e.src_path) == os.path.dirname(e.dest_path) \
                and os.path.abspath(e.dest_path) in self.watched:
            subprocess.run("python " + e.dest_path)


save_handler = SavedFileHandler(watchpats=sys.argv[1:])
observer = Observer()
observer.schedule(save_handler, ".", recursive=True)

with observer:
    try:
        while True:
            time.sleep(20)
    except KeyboardInterrupt:
        print("Received interrupt, quitting...", file=sys.stderr)