using-streamlit-session-state

What problem does it solve?

Streamlit reruns the entire script on every interaction, resetting non-persistent variables. This Skill shows how to use st.session_state to persist values across reruns, enabling stable, per-user experiences.

Core Features & Use Cases

• Persist widget state across reruns by linking widgets to session_state via keys.
• Initialize and safely access session data, avoiding KeyError and race conditions.
• Implement per-page or multi-page state sharing and robust callbacks.

Quick Start

Set up initial state with st.session_state.setdefault("key", default), attach widgets with a key parameter (e.g., st.text_input("Name", key="user_name")), then read and update state from st.session_state in your callbacks and page logic.