Flask is awesome

  from flask import Flask
  app = Flask(__name__)
  
  @app.route("/")
  def hello():
      return "Hello World!"

  if __name__ == "__main__":
      app.run()

  require 'sinatra'

  get '/hi' do
    "Hello World!"
  end

I hereby dub this the programmer equivalent of "sharp knees".

Explanation from the ever inimitable Urban Dictionary:

"A judgment leveled against an otherwise perfectly proportioned, if not slightly trim, and pleasant looking woman. Generally uttered by a male who is way below her class."

This comment is otherwise beneath a reasoned response.

The intention wasn't to diss Flask. It is a very concise and useful framework. All the comments apply to my original comparison.

  public static void main(..){
    System.out.println("Hello World");
  }

  print "Hello World"

In Flask I need to instantiate the Flask app, define a function to run and decorate it with a route. That raises all sorts of questions about what a decorator is (which for a casual pythonist may or may not be something they understand - I know my understanding of decorators is sketchy at best). Then I need to explicitly call app.run() somewhere.

In Sinatra, the DSL makes it much simpler. If I receive a "get '/'" request, then "do" the following stuff. "end".

Flask is very concise. No doubt about it. It's stripped down to it's very minimum. Yet Sinatra manages to be even simpler, which is impressive to me.

We are developing a web service with it, and as our project has grown we have had no problems moving from decorated functions to class based views.

We looked at Django but quickly realised that our service didnt need to be that heavy.

And because of its Flasks clear modularity, unit and functional testing things has been fairly easy.

One example that was annoying me recently was in trying to select a Javascript client-side MVC (MVVM, etc.) framework for a single-page application.

The internet is full of people busily comparing, contrasting, arguing about, and recommending JS frameworks. Problem: 95% of them are doing so based on a < 100 line demo app, usually implementing a todo list, often which makes implausible simplifying assumptions. "Hm, that's nice, but check out the demo todo list app for MagicJS! It's 57 characters shorter, and the code forms the shape of a flower, and it would be quite easy to extend it to let you create new items!""

No real world app is going to be solved in < 100 lines[1], and while it's awesome to know that you've chosen a framework which can be used to create incredibly elegant < 100 line demo apps, what I really care about is how the framework works for large apps. Scale (in the sense of scaling up from the example code on the frameworks homepage to a real app that actually handles all the corner cases) matters HUGELY. And I don't think that gets nearly enough recognition.

(In fact, on this very thread, I see someone comparing a "hello world" app in Flask and Sinatra, and complaining about Flask's relative "verbosity". This is utter nonsense of the precise kind you've identified. Implement a calendar app in both that syncs with Google Calendar, and THEN compare line counts, and NOW you have a some feel for verbosity. Sinatra might win handily, but you can't tell that from a hello world app. Then again, off the top of my head, I can't think of one actually useful thing a hello world app can tell you about a framework.)

[1]: I'm speaking figuratively, obviously. Some of my proudest moments as a programmer have involved solving problems in just a couple. Sadly, this does not happen often. :)