Creating URL using url_for in Flask

In this post I quickly show how the url_for command allows us to generate URLs. It isn’t a fundamental feature, but it can save you some boilerplate.

import requests
import io

from flask import Flask, url_for

app = Flask(__name__)

@app.route('/card/<int:card_id>')
def card(card_id):
    return f'Card({card_id})'

with app.test_request_context():
    for i in range(10):
        print(url_for('card', card_id=str(i)))

if __name__ == '__main__':
    app.run(debug=True)

The function test_request_context is described in its API documentation as follows:

Create a RequestContext for a WSGI environment created from the given values. This is mostly useful during testing, where you may want to run a function that uses request data without dispatching a full request.

Indeed, if you look at the CLI output from running the application you will see something like this:

/card/0
/card/1
/card/2
/card/3
/card/4
/card/5
/card/6
/card/7
/card/8
/card/9

While this is a simple example. you can use url_for to create more complicated URLs and content.