using-streamlit-session-state

Persist variables across Streamlit reruns by assigning them to st.session_state, which maintains values between script executions and ensures stable widget behavior without resetting.

The best way to initialize Streamlit session state safely is using a setdefault-based pattern, which establishes per-user session defaults and guards against uninitialized keys during app interactions.

Mixing value parameters with session state in Streamlit widgets causes conflicts because the widget receives conflicting initialization sources, so map widgets directly to session_state keys instead.

Use callbacks to update Streamlit session state by binding functions to widget interactions, allowing state values to change in response to user actions without triggering re-render issues.

Yes, Streamlit session state supports per-user session isolation in multi-page apps, ensuring that state variables remain independent and scoped to each specific user browser session.

Associate Streamlit widgets with session state keys by passing the key parameter to the widget, enabling seamless value sharing where the widget reads and updates the mapped state automatically.