Open browser automatically when Python code is executed

I'd suggest the following improvement to allow for loading of the browser when in debug mode:
Inspired by this answer, will only load the browser on the first run...

def main():
    
    # The reloader has not yet run - open the browser
    if not os.environ.get("WERKZEUG_RUN_MAIN"):
        webbrowser.open_new('http://127.0.0.1:2000/')

    # Otherwise, continue as normal
    app.run(host="127.0.0.1", port=2000)

if __name__ == '__main__':
    main()

https://stackoverflow.com/a/9476701/10521959

Use timer to start new thread to open web browser.

import webbrowser
from threading import Timer

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

def open_browser():
      webbrowser.open_new('http://127.0.0.1:2000/')

if __name__ == "__main__":
      Timer(1, open_browser).start();
      app.run(port=2000)