app.py

import streamlit as st
import pandas as pd
import numpy as np
import plotly.express as px
import random
from datetime import datetime

# Set page configuration
st.set_page_config(
    page_title="Quick Streamlit Demo",
    page_icon="📊",
    layout="wide",
    initial_sidebar_state="expanded"
)

# Add custom CSS
st.markdown("""
<style>
    .main-header {
        font-size: 2.5rem;
        color: #1E88E5;
    }
    .sub-header {
        font-size: 1.5rem;
        color: #424242;
    }
</style>
""", unsafe_allow_html=True)

# App title
st.markdown('<p class="main-header">Interactive Streamlit Dashboard</p>', unsafe_allow_html=True)
st.markdown("This is a quick demo of Streamlit's capabilities.")

# Sidebar
st.sidebar.title("Controls")
data_size = st.sidebar.slider("Data Points", 10, 500, 100)
chart_height = st.sidebar.slider("Chart Height", 300, 800, 400)

# Define color themes dictionary mapping to actual Plotly color sequences
color_themes = {
    "blues": px.colors.sequential.Blues,
    "reds": px.colors.sequential.Reds,
    "greens": px.colors.sequential.Greens,
    "purples": px.colors.sequential.Purples,
    "oranges": px.colors.sequential.Oranges
}

color_theme = st.sidebar.selectbox("Color Theme", list(color_themes.keys()))

# Generate random data
@st.cache_data
def generate_data(n_points):
    np.random.seed(42)
    dates = pd.date_range(start=datetime.now().date(), periods=n_points)
    df = pd.DataFrame({
        'date': dates,
        'value': np.random.randn(n_points).cumsum(),
        'category': np.random.choice(['A', 'B', 'C', 'D'], n_points),
        'size': np.random.randint(10, 100, n_points)
    })
    return df

# Create tabs
tab1, tab2, tab3 = st.tabs(["Chart", "Data Explorer", "About"])

with tab1:
    st.markdown('<p class="sub-header">Interactive Data Visualization</p>', unsafe_allow_html=True)
    
    # Generate and display data
    df = generate_data(data_size)
    
    # Create a line chart with Plotly
    fig = px.line(
        df, x='date', y='value', 
        color='category', 
        color_discrete_sequence=color_themes[color_theme],
        height=chart_height
    )
    fig.update_layout(
        title="Time Series Data",
        xaxis_title="Date",
        yaxis_title="Value",
        legend_title="Category",
        hovermode="x unified"
    )
    st.plotly_chart(fig, use_container_width=True)
    
    # Add some metrics
    col1, col2, col3, col4 = st.columns(4)
    with col1:
        st.metric("Max Value", f"{df['value'].max():.2f}", f"{random.uniform(-10, 10):.2f}%")
    with col2:
        st.metric("Min Value", f"{df['value'].min():.2f}", f"{random.uniform(-10, 10):.2f}%")
    with col3:
        st.metric("Average", f"{df['value'].mean():.2f}", f"{random.uniform(-10, 10):.2f}%")
    with col4:
        st.metric("Data Points", len(df), f"{data_size - 50}")

with tab2:
    st.markdown('<p class="sub-header">Data Explorer</p>', unsafe_allow_html=True)
    
    # Filter options
    st.subheader("Filter Data")
    
    # Create columns for filters
    filter_col1, filter_col2 = st.columns(2)
    
    with filter_col1:
        selected_categories = st.multiselect(
            "Select Categories",
            options=df['category'].unique(),
            default=df['category'].unique()
        )
    
    with filter_col2:
        min_val, max_val = st.slider(
            "Value Range",
            float(df['value'].min()),
            float(df['value'].max()),
            [float(df['value'].min()), float(df['value'].max())]
        )
    
    # Filter the data
    filtered_df = df[
        (df['category'].isin(selected_categories)) &
        (df['value'] >= min_val) &
        (df['value'] <= max_val)
    ]
    
    # Show the filtered dataframe
    st.subheader(f"Filtered Data ({len(filtered_df)} rows)")
    st.dataframe(filtered_df, use_container_width=True)
    
    # Download button
    csv = filtered_df.to_csv(index=False).encode('utf-8')
    st.download_button(
        "Download CSV",
        csv,
        "filtered_data.csv",
        "text/csv",
        key='download-csv'
    )

with tab3:
    st.markdown('<p class="sub-header">About This App</p>', unsafe_allow_html=True)
    
    st.markdown("""
    This is a quick demo showcasing some of Streamlit's features:
    
    - **Interactive Charts**: Visualize data dynamically
    - **Data Filtering**: Filter and explore datasets
    - **Download Capabilities**: Export data as CSV
    - **Metrics & KPIs**: Display key performance indicators
    - **Custom Styling**: Enhance UI with custom CSS
    
    Streamlit makes it easy to create data apps with just a few lines of Python code.
    """)
    
    st.info("Made with ❤️ using Streamlit")

# Footer
st.markdown("---")
st.markdown("Created as a quick Streamlit demo")