Flask_hello_world.py

# Import Flask 
from flask import Flask, render_template.

# create instance of the class
app=Flask(__name__)

# Guides flask which url should be running first.
# '/' ==> root page
@app.route('/') 
def index():
    return render_template('index.html')
    
if __name__=="__main__":
  app.run(debug=True,port=5000)