Flask-framework: MVC pattern

Flask is actually not an MVC framework. It is a minimalistic framework which gives you a lot of freedom in how you structure your application, but MVC pattern is a very good fit for what Flask provides, at least in the way that MVC pattern is understood today in the context of web applications (which purists would probably object to).

Essentially you write your methods and map them to specific route, e.g.:

@app.route("/")def hello():    return "Hello World!"

No view or model there, as you can see. However, it is also built on top of Jinja2 template library, so in a realistic app, your method (which acts as a controller) looks like:

@app.route("/")def hello():    return render_template('index.html', username="John Doe")

Here, you use index.html template to render the page. That is your view now.

Flask doesn't prescribe any model. You can use whatever you want - from complex object models (typically with using some ORM like SQLAlchemy) to simplest thing which fits your needs.

And there you have it: MVC

To look at Flask from a MVC perspective, I think Flask gives us flexibility to implement our own Model or Views. But for the Controller we need to rely on the Flask framework itself.

1. @app.route("/")2.     def hello():2.1        # Code for your model here2.2        # model code3.         return render_template('index.html', username="John Doe")

In the above code -

1. line 1 - (invoked by) Controller: is what the Flask Controller calls,
2. line 2 - Model: this is where we code our own implementation for defining the Model,
3. line 3 - View: we can code our View as index.html coded with {{ }} and {% %} with Model data being passed to View as form of Dict or user object. e.g.username="Xxx"