from threading import Thread from sys import stderr import flask t = None app = flask.Flask(__name__) counter = 0 @app.route('/') def main(): return f'Hello {counter}' def serve(): global t if t is None: t = Thread(target=app.run, kwargs={'port': 8448}) t.start() print('So I kinda started', flush=True, file=stderr) if __name__ == '__main__': serve()