Often I get asked by fellow python developers why I chose Django/Flask for a particular project (usually by someone who prefers the framework I didn’t choose 😉). I think both frameworks are excellent and are well suited for a variety of use cases.

So how do I decide which to use for a new project? I found a simple heuristic to get 90% of the way to a final decision, and it’s pretty easy to follow:

Decide what features your project needs:

• User accounts
• An Object Relational Manager (ORM)
• Database Migrations
• User registration/social authentication
• An admin site

Does your project require 2 or more of these features?

If Yes => Choose Django

If No => Choose Flask

Flask is great for small, focused projects. Think microservices, APIs, or very small websites. But once you have to start hunting down and installing extensions like Flask Sqlalchemy and Flask User you quickly enter a situation where the “batteries included” approach of Django makes more sense. You are basically spending time re-implementing stuff that larger frameworks like Django ship with out the box, and that are very well integrated.

On the other hand, Django can be a huge overkill for some projects. Think of an API that accepts image uploads and returns thumbnails. You could use Django for such a task, but the amount of boilerplate and setup required would be ridiculous. One of the great things about Flask is the fact that an entire webapp can be written in a single file.

Of course like I said this heuristic only gets you 90% of the way. Every project has unique use cases and design constraints that must be taken into account before making a large decision like which tech stack to use.