🐍 Streamlit for Absolute Beginners: Build Web Apps with Just Python

If you’re new to coding or just starting with Python, Streamlit is the easiest way to build interactive web apps — no HTML, CSS, or JavaScript needed. This guide walks you through everything you need to know, with simple explanations and examples.

📦 What Is Streamlit?

Streamlit is a Python library that lets you create web apps using just Python scripts. It’s widely used for:

• Data science dashboards
• Machine learning model demos
• Interactive tools and prototypes

🛠️ Installation

Open your terminal and run:

pip install streamlit

To check if it’s installed:

streamlit hello

▶️ Your First App

Create a file called app.py:

import streamlit as st

st.title("Hello, Streamlit!")
st.write("This is your first web app.")

Run it with:

streamlit run app.py

🧱 Streamlit Basics

Here are the most common Streamlit functions:

🎛️ Widgets for Interactivity

Widgets let users interact with your app:

name = st.text_input("Enter your name")
if name:
    st.write(f"Hello, {name}!")

Other widgets:

• st.button("Click me")
• st.checkbox("I agree")
• st.radio("Choose one", ["A", "B", "C"])
• st.selectbox("Pick one", ["Apple", "Banana"])
• st.slider("Choose a number", 0, 100)
• st.date_input("Pick a date")
• st.file_uploader("Upload a file")

📊 Displaying Data

Streamlit makes it easy to show data:

import pandas as pd
import numpy as np

df = pd.DataFrame(np.random.randn(10, 2), columns=["A", "B"])
st.dataframe(df)
st.line_chart(df)
st.bar_chart(df)

📁 Upload and Display Files

uploaded_file = st.file_uploader("Choose a file")
if uploaded_file is not None:
    st.write("File uploaded successfully!")

You can also read CSVs:

import pandas as pd

df = pd.read_csv(uploaded_file)
st.dataframe(df)

🧠 Caching for Speed

Use @st.cache_data to avoid reloading data every time:

@st.cache_data
def load_data():
    return pd.read_csv("data.csv")

df = load_data()

🧭 Sidebar Navigation

st.sidebar.title("Navigation")
option = st.sidebar.selectbox("Choose a page", ["Home", "About"])
if option == "Home":
    st.write("Welcome to the Home page!")

📐 Layouts and Columns

col1, col2 = st.columns(2)
col1.write("Left column")
col2.write("Right column")

🧪 Displaying Code and JSON

st.code("for i in range(5): print(i)")
st.json({"name": "Alice", "age": 30})

📤 Exporting Results

You can let users download files:

st.download_button("Download CSV", df.to_csv(), "data.csv")

🌐 Deployment

Deploy your app for free using:

🧠 Bonus:

Here are some beginner-friendly tips inspired by GeeksforGeeks:

• Use st.form() for grouped inputs and submission buttons
• Use st.progress() and st.spinner() for long tasks
• Use st.session_state to store user inputs across interactions
• Use st.experimental_rerun() to refresh the app programmatically