Refactoring Databutton Code for Production

Databutton apps often have data processing logic mixed directly into FastAPI route handlers rather than separated into reusable functions. Python scripts for data transformation tend to grow long with no clear structure

Extract data processing logic into separate Python modules with pure functions that take dataframes as input and return processed data. Route handlers should only handle HTTP concerns (request parsing, response formatting) and call service functions. This makes testing and reuse much simpler

Not all Databutton code needs refactoring. If it works, is secure, and you don't need to modify it, leave it alone. Refactor when: you need to add features and the current structure makes it difficult, bugs keep appearing in the same area of code, or onboarding new developers takes too long because the code is hard to understand.

The golden rule of refactoring: behavior stays the same, structure changes. Before refactoring any code, make sure you have tests covering the current behavior (or add them first). Refactor in small steps — change one thing at a time and verify the app still works. Use version control (git) to commit after each successful change so you can revert if something breaks.

A well-organized project has a predictable structure where anyone can find what they're looking for. Group files by feature (not by type), keep related code together, and use clear naming. Every file should have a single clear purpose. If you can't describe what a file does in one sentence, it's probably doing too much and should be split.