Learning Flask With a Personal Project
What is Flask?
Flask is a web framework written in Python. It is a microframework that does not require particular tools or libraries. As such, Flask does not come with database abstraction layer, form validation nor any other components, unlike Django. Flask and Django are the most popular Python webdev frameworks, so supports for both are extensive.
Flask Components
Flask operates with these components.
- Werkzeug, a toolkit for Web Server Gateway Interface (WSGI)
- Jinja, a template engine for displaying Python variables in markup
- MarkupSafe, a string handling library that escape characters so it is safe to use HTML and XML
- ItsDangerous, a data serialization library used to store Flask app sessions without allowing users to tamper with session contents
Toy Project – Pack Cracking Simulator
The toy project is a simple web application that simulates the opening of a card game booster pack, or colloquially called ‘pack cracking’. A Magic: The Gathering pack (only the best trading card game in the world) is cracked open, revealing 16 cards. A standard MTG pack (not counting special products) will contain 1 rare or mythic rare card, 3 uncommon cards, 11 common cards, and a token card. Promotional cards are not counted since they do not provide any gameplay value.
Setting Up the Flask Project
Setting up a Flask project can be a daunting task for new web developers who are not familiar with the Flask project structure. Instead, running a boilerplate generator is faster and much more convenient. The one used in this project is https://github.com/isakal/create-flask-app, a Flask version of the popular Create React App generator. Spending time for development is much more productive than spending time on project configuration.
Card Data Request
Card data is acquired using the Scryfall API. Scryfall is the most well known search engine for Magic: the Gathering cards. Requests for sets and individual cards can be performed by following the request format stated in the docs. The response will be returned as JSON blobs.
As per usage policy, each request comes with a 50 milliseconds delay so that the Scryfall server does not experience heavy load.
Since all request information can be contained inside the URL, all Scryfall requests are GET requests.
Request Caching
Sending a set request to the Scryfall API, getting the JSON blob and rendering the cards takes around 12 to 20 seconds, which is quite slow for a simple app. Caching the requests would bypass the need for the application to fetch data from Scryfall’s server. With the cache, the first request takes more time, but subsequent requests of the same set would take a mere fraction of a second.
Since this is a simple app, there is no need for long term storage nor a sophisticated caching policy. Setting request TTLs to one day will wipe out stale data.
Architecture
The application works as follows:
1.) The user selects the set with the interface.
2.) The application sets a get request to the Scryfall API.
3.) If the GET request is cached, get the JSON blob from the cache, send it to the web server,
and render the cards on the browser. Else, get the data from the server, cache the request, and send the data to the web server before rendering it on the browser.