when use flask code example

Example 1: flask example

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

Example 2: what is flask

These are by far the best Flask tutorials there are: https://youtube.com/playlist?list=PLzMcBGfZo4-n4vJJybUVV3Un_NFS5EOgX