this should work. Flask hello world

app.py

from flask import Flask, render_template, request

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def hello():
  # respond only if the method is POST
  # i.e. user clicked submit
  if request.method == 'POST':
    name=request.form.get('name', 'world')
    return f'hello {name}'
  
  # otherwise respond with the form
  return '''
<form action="/" method="POST">
  <input name="name" />
  <input type="submit">
</form>
'''

if __name__ == '__main__':
  app.run(host='0.0.0.0', port=3000)