using-streamlit-session-state

To persist variable values across Streamlit reruns, use st.session_state, a dictionary-like object that stores per-user data and prevents variables from resetting on each interaction.

Streamlit widgets reset their values because the script reruns top-to-bottom on every interaction. You can sync widget values to session state by assigning a key parameter to the widget.

The best way to initialize state in a Streamlit multi-page app is using the setdefault method on st.session_state, which provides a safe and predictable starting point for per-user state without overwriting existing values.

Yes, you can use session state to manage per-user and per-tab data in Streamlit. It enables stable experiences across interactions and pages by isolating state for each user session.

Callbacks in Streamlit work with st.session_state by synchronizing widget values through the key parameter, allowing you to read and modify state safely when a widget value changes during a rerun.