organizing-streamlit-code

To organize Streamlit app code, you separate UI from business logic by placing UI components in streamlit_app.py and moving logic into utility modules under a utils/ directory to improve maintainability and readability.

The best way to structure a growing Streamlit project is adopting a clear directory layout with UI in streamlit_app.py, page modules under app_pages/, and utilities under utils/ to simplify cross-page reuse and collaboration.

You should avoid __main__ guards in Streamlit UI code because the framework executes scripts top-down automatically, and keeping guards out of UI modules ensures modular components run correctly during cross-page reuse and testing.

Yes, separating UI from logic in Streamlit makes business logic easier to test because moving logic into dedicated utility modules under utils/ removes UI clutter and allows direct testing of the underlying functions.

You need to modularize your Streamlit application when your project starts growing and requires scalable structure, cross-page component reuse, and testable business logic separated from the UI layer to avoid single-file clutter.