How to style your Streamlit App with Custom Themes

📘 Introduction

Streamlit makes it easy to turn Python scripts into interactive web apps — no front-end coding needed. But what if you want to adjust the look and feel? Maybe you want a dark theme, different fonts, or brand colors.

The good news: Streamlit has a built-in theme system that lets you style your app with just a small configuration file. In this tutorial, you’ll learn how to build a basic app, run it, and then give it a custom theme.

✅ Prerequisites

Before starting, make sure you have the following:

🐍☑️ Python installed
📦☑️ Pip installed
🌐☑️ A virtual environment (venv) created and activated

📦1️⃣ Install Libraries

Install the following Python packages using pip:

pip install streamlit pandas numpy

📥2️⃣ Import Libraries

Start by importing the required Python modules:

import streamlit as st
import pandas as pd
import numpy as np

✍️3️⃣ Create a Basic App

First, let’s create a simple app and run it.

Create a file called app.py and add the following code:

import streamlit as st
import pandas as pd
import numpy as np

st.title("Themed Streamlit App 🎨")
st.write("This app demonstrates how to use Streamlit themes.")

# Add a slider
points = st.slider("Select number of points", 10, 100)

# Generate random data
data = pd.DataFrame({
    'x': np.arange(points),
    'y': np.random.randn(points).cumsum()
})

# Show a line chart
st.line_chart(data.set_index('x'))

Now run your app from the terminal: