import url_for flask code example

Example 1: flask how to run app

$ export FLASK_APP=hello.py
$ python -m flask run
 * Running on http://127.0.0.1:5000/

Example 2: default flask app

from flask import Flask
app = Flask(__name__)

@app.route('/')
def index():
    return 'Flask'

Example 3: flask url_for external

url_for(..., _external=True)