using-streamlit-session-state

To persist UI state across Streamlit reruns, initialize a default value in st.session_state and bind it to your widget. This prevents variables from resetting each time the script executes from top-to-bottom.

Streamlit widget values reset because the script reruns top-to-bottom on every interaction. Without using st.session_state to explicitly persist values, variables lose their state and revert to defaults.

The best way to manage session state initialization in Streamlit is using safe access patterns with st.session_state. Initialize default values safely before binding them to widgets to ensure predictable behavior and cross-widget consistency.

Trigger state updates with Streamlit callbacks using the on_change and on_click parameters. These callback mechanisms allow you to execute functions that update st.session_state reliably when a user interacts with a widget.

Yes, st.session_state ensures per-user state isolation in Streamlit applications. It maintains independent UI state for each user session, preventing state collisions across different concurrent users.

Common pitfalls when using Streamlit session state include improper initialization patterns and cross-widget inconsistency. Safely binding widgets to st.session_state and using callbacks correctly helps avoid unpredictable behavior.