Streamlit Session State: The Essential Guide to Get Started
- Name
- Olaf Källström
Published on
Streamlit has revolutionized the way we approach web development, especially in the realm of data science and machine learning. One of its most powerful features is the Session State. This article aims to provide a comprehensive guide on Streamlit Session State, its usage, benefits, and how it compares to other state management tools.
Have you heard of this awesome Data Analysis & Data Visualisation tool, that turns your Streamlit App into Tableau?
PyGWalker (opens in a new tab) is a Python Library that helps you easily embed a Tableau-like UI into your own Streamlit app effortlessly.
Introduction to Streamlit and Session State
What is Streamlit?
Streamlit is an open-source Python library that allows developers to create interactive web applications with ease. It's particularly popular among data scientists and machine learning engineers due to its simplicity and the ability to create data-driven web applications rapidly.
Understanding Session State in Streamlit
In the context of web development, a session refers to the period that a user interacts with a web application. The data that the application stores about this user interaction is known as the Session State. In Streamlit, the Session State allows developers to maintain data across reruns, enabling the creation of more interactive and dynamic applications.
Utilizing Streamlit Session State
Quickly Get Started with Streamlit Session State
Using Streamlit Session State is straightforward. It allows you to store data that persists across reruns of the application. For instance, if you want to store a user's input from a text input widget, you can store it in the session state. Here are the steps:
- Install Streamlit if you haven't already:
pip install streamlit - Create a new Python file and import Streamlit:
import streamlit as st - Initialize your session state:
if 'my_var' not in st.session_state: st.session_state['my_var'] = 0 - Use your session state in your app:
st.session_state['my_var'] += 1
Here is the sample code:
import streamlit as st
if 'user_input' not in st.session_state:
st.session_state['user_input'] = ''
user_input = st.text_input("Enter some text")
if user_input:
st.session_state['user_input'] = user_input
st.write(f"You entered: {st.session_state['user_input']}")In this example, the user's input is stored in the session state and persists even if the application reruns.
Beyond the Basics: Advanced Use Cases and Best Practices
Once you've got the basics down, the real fun begins. Streamlit Session State opens up a world of advanced use cases. For instance, you can use it to store user authentication information. Here's a simple example:
if 'username' not in st.session_state:
st.session_state['username'] = ''
username = st.text_input("Enter your username")
if username:
st.session_state['username'] = username
st.write(f"Hello, {st.session_state['username']}!")In this example, the user's username is stored in the session state and persists even if the application reruns.
Remember, with great power comes great responsibility. It's crucial to manage your session state effectively to ensure your application runs like a well-oiled machine.
Unleashing the Power of Streamlit Session State
Streamlit Session State: A Game-Changer in Web Development
Streamlit Session State is a game-changer in web development. It allows for the creation of dynamic, interactive applications as data can persist across reruns. This is a godsend for applications that require user input or have multiple stages or steps.
Streamlit Session State: A Secret Weapon in Machine Learning and Data Science
In the world of machine learning and data science, Streamlit Session State is the secret weapon you didn't know you needed. It can be used to store everything from:
- Model parameters
- User inputs for data filters
- Intermediate data processing results
This means you can avoid unnecessary computations and supercharge the performance of your application.
The Fine Print: Performance and Limitations of Streamlit Session State
While Streamlit Session State is a powerful tool, it's also important to be aware of its limitations. The session state is stored in memory, so it can increase the memory usage of your application. Therefore, it's crucial to manage the session state properly and avoid storing large amounts of data that could lead to performance issues.
Streamlit Session State vs Other State Management Tools
Comparison: Streamlit Session State vs st.cache
Streamlit offers another feature for state management: st.cache. While both st.cache and Session State allow you to store data across reruns, they serve different purposes. st.cache is designed to cache the results of long-running computations to improve performance, while Session State is designed to store user interaction data across reruns.
Here's a simple example of using st.cache:
@st.cache
def expensive_computation():
# Some expensive computation goes here
return result
result = expensive_computation()In this example, the result of the expensive computation is cached and reused in subsequent reruns, improving the performance of the application.
Have you heard of this awesome Data Analysis & Data Visualisation tool, that turns your Streamlit App into Tableau?
PyGWalker (opens in a new tab) is a Python Library that helps you easily embed a Tableau-like UI into your own Streamlit app effortlessly. Check out this amazing video produced by Sven from Coding is Fun (opens in a new tab) demonstrating the detailed steps for empowering your Streamlit app with this powerful Data Visualization Python Library!
Special Thanks to Sven and his great contribution (opens in a new tab) to PyGWalker community!
Additionally, you can also check out PyGWalker GitHub Page (opens in a new tab) for more PyGWalker examples.
Streamlit Session State vs Redux: A Detailed Analysis
Redux is a popular state management library for JavaScript applications, particularly those built with React. It provides a centralized store for state that needs to be used across your entire application, with rules ensuring that the state can only be updated in a predictable fashion.
On the other hand, Streamlit Session State is a feature of the Streamlit library that allows data to persist across reruns of the application. It's primarily used in server-side Python applications for creating interactive and dynamic web applications.
While both Redux and Streamlit Session State serve the same purpose of managing state, they are used in different contexts and have different features:
- Programming Language: Redux is used with JavaScript, while Streamlit Session State is used with Python.
- Application Type: Redux is typically used in client-side applications, while Streamlit Session State is used in server-side applications.
- State Persistence: In Redux, the state persists as long as the user is on the website or until the state is explicitly cleared. In Streamlit, the session state persists across reruns of the application, but it's cleared when the user closes the application.
- Learning Curve: Redux has a steeper learning curve due to its concepts like reducers, actions, and middleware. Streamlit Session State, on the other hand, is simpler and easier to use, especially for those already familiar with Python.
Streamlit Session State vs Local Storage and Context API
Local Storage and the Context API are other state management solutions used in JavaScript applications.
Local Storage is a web storage object that allows you to store data persistently in the user's browser. The data stored in Local Storage has no expiration time, and it remains even after the browser is closed and reopened. It's useful for storing small amounts of data like user preferences or session data.
The Context API, introduced in React 16.3, allows you to share data that can be considered "global" for a tree of React components, such as the current authenticated user, theme, or language. It's designed to share data that can be considered global for a tree of React components.
While these tools are powerful in their own right, they are not directly comparable to Streamlit Session State as they are used in different programming languages and application contexts:
- Programming Language: Both Local Storage and Context API are used with JavaScript, while Streamlit Session State is used with Python.
- Data Persistence: Local Storage allows data to persist even when the browser is closed and reopened, while the Context API and Streamlit Session State do not have this feature.
- Use Cases: Local Storage is useful for storing small amounts of data like user preferences or session data. The Context API is useful for sharing global data across a tree of React components. Streamlit Session State is useful for storing data that needs to persist across reruns of the application.
Handling Complex Data Types in Streamlit Session State
Streamlit Session State is not just limited to storing simple data types like integers or strings. It can also handle complex data types like lists, dictionaries, sets, and even custom objects. This makes it a versatile tool for managing state in your Streamlit applications.
For instance, you can store a list of user inputs in the session state:
if 'user_inputs' not in st.session_state:
st.session_state['user_inputs'] = []
user_input = st.text_input("Enter some text")
if user_input:
st.session_state['user_inputs'].append(user_input)
st.write(f"You entered: {st.session_state['user_inputs']}")In this example, every time the user enters some text, it's added to a list stored in the session state.
Conclusion
Streamlit Session State is a powerful tool for managing state in your Streamlit applications. It allows you to create more interactive and dynamic applications by storing data across reruns. Whether you're a beginner just starting out with Streamlit or an experienced developer looking to optimize your applications, understanding and effectively using Session State can significantly enhance your web development process.
Frequently Asked Questions
What is Session State in Streamlit?
Session State in Streamlit is a feature that allows data to persist across reruns of the application. It's used to store data about user interactions, making it possible to create more interactive and dynamic applications.
What are the disadvantages of Streamlit?
While Streamlit is a powerful tool for creating interactive web applications, it does have a few limitations. For instance, it's primarily designed for prototyping and may not be suitable for building complex, large-scale web applications. Also, as it's a relatively new library, it may lack some features found in more mature web development frameworks.
Do Streamlit sessions expire?
Streamlit sessions do not expire on their own. However, the data in the session state is cleared when the user closes the application.
How to use session state in asp.net?
Session state in ASP.NET is a feature that allows you to store and retrieve user-specific values temporarily. You can use it by calling the Session object and assigning values to it, like Session["UserName"] = "John Doe";. Note that this is different from Streamlit Session State, which is used in Python applications.