1 Session State Explained

Key Concepts

• Session State: A way to store and manage user-specific data across multiple interactions within a Streamlit app.
• st.session_state: A Streamlit object that provides access to the session state.
• State Persistence: The ability to maintain state across reruns of the Streamlit app.
• User Interaction: How session state helps in managing user interactions and data.

Explanation

1. Session State

Session state in Streamlit is a mechanism to store and manage user-specific data across multiple interactions within a single session. This allows the app to remember the state of widgets and other elements between reruns.

2. st.session_state

st.session_state is a Streamlit object that provides access to the session state. You can use this object to store and retrieve data that needs to persist across reruns of the app.

3. State Persistence

State persistence refers to the ability of the session state to maintain its values across reruns of the Streamlit app. This is crucial for creating interactive apps where user inputs and other data need to be preserved.

4. User Interaction

Session state helps in managing user interactions by allowing the app to remember the state of widgets and other elements. This makes the app more responsive and user-friendly.

Examples

Example 1: Basic Session State

import streamlit as st

if 'counter' not in st.session_state:
    st.session_state.counter = 0

increment = st.button('Increment')
if increment:
    st.session_state.counter += 1

st.write('Counter:', st.session_state.counter)
    

Example 2: Session State with Multiple Widgets

import streamlit as st

if 'name' not in st.session_state:
    st.session_state.name = ''

if 'age' not in st.session_state:
    st.session_state.age = 0

st.text_input('Enter your name', key='name')
st.number_input('Enter your age', key='age')

st.write('Name:', st.session_state.name)
st.write('Age:', st.session_state.age)
    

Analogies

Think of session state as a sticky note that you use to remember important information during a meeting. Each time you come back to the meeting, the sticky note still has the information you wrote down, allowing you to pick up where you left off. Similarly, session state in Streamlit allows the app to remember user interactions and data across reruns.

By mastering session state in Streamlit, you can create more interactive and user-friendly applications that provide a seamless experience for users.