Streamlit-state-model - use session_state with normal python classes

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I love Streamlit, but working with st.session_state can be tedious. Coming from an OOP background, I cringe at managing each key in st.session_state individually, checking if it exists, and losing intellisense for names and types.

So I made streamlit-state-model which offers a base class StateModel that you can subclass to push your class’ attribute I/O directly into st.session_state. This means you define what should exist in st.session_state once in the form of a normal python class, and then access those values anywhere in your Streamlit app through an instance of the class with the expected statefulness of st.session_state.

Features

  • Persistence: Class instance storage is pushed to st.session_state so class attribute values are retained across page refreshes and switches (in multi-page apps).

  • Easy Setup: StateModel can be used with existing or new class definitions.

  • Default Values: Define the default state of st.session_state with normal class’ default annotations and gain the ability to reset them all to defaults with a single function call.

  • Debugging: When debugging, you can now see the current values in st.session_state by inspecting your class’ attribute values.

  • Intellisense Support: Retain normal docstrings and type intellisense that you normally lose when working with st.session_state.

  • Inline Integration: Declare your class instance inline with the rest of your code and eliminate spaghetti if checks around current state of st.session_state.

  • Docstring Access: Retrieve attribute docstrings via the docstrings dictionary within your app.

Getting Started

Install the package using pip:


pip install streamlit-state-model

Take your existing class and subclass StateModel:


import streamlit_state_model as ssm

class Session(ssm.StateModel):

  favorite_color: str = "#252D3D"
  
  "The user's favorite color as a hex string."
  
  favorite_number: int = 0
  
  "The user's favorite number."

At the entry point of your app, initialize your class in “build” mode.


# streamlit_app.py

session = Session(mode="build")

st.write(session.favorite_number) # outputs default value of 0

session.favorite_number = 1 # set to a new value

Anywhere else in your app you can initialize in lazy (default) mode to access current values:


# pages/page_1.py

session = Session() # init in lazy mode

st.write(session.favorite_number) # outputs 1 as set in streamlit_app.py

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Would love to hear feedback on this idea! I have used it extensively on huge Streamlit apps and multiple StateModels and it has been a huge success and time saver.

Feel free to drop on over to trenton-ftw/streamlit-state-model for more info and to review the source. Explore our demo Streamlit app for an example of integrating StateModel into a multipage app on Streamlit Community Cloud at state-model-demo-app.

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Signed up to the forum just to say I love this! I’ll be sure to submit issues/feedback over on the repo if I have any. Cheers.