organizing-streamlit-code

To separate UI logic from business logic in a Streamlit app, move data loading and processing into utility modules while keeping only Streamlit UI calls in the main streamlit_app.py and app_pages directory. This modular structure supports scalable single-file or multi-page projects.

A recommended Streamlit directory layout uses a main streamlit_app.py for entry, an app_pages folder for page modules, and a utils folder for reusable logic. This structure organizes code for clarity and enables easier imports.

Avoiding __main__ guards in Streamlit app entry files prevents execution barriers during module imports, ensuring that page modules and tested utility functions load correctly. This maintains testability and incremental changes.

You can unit test business logic from a single-file Streamlit script by extracting data processing and API calls into separate utility modules. This allows you to import and test helper functions independently of the UI.

Split complex logic into modules when your Streamlit app grows beyond a simple script and accumulates data processing or API calls. This separation makes the codebase easier to read, test, and maintain.