Plotly

Plotly: Interactive Graphing Library

Overview
Plotly (specifically `plotly.express` and `plotly.graph_objects`) is a graphing library that makes interactive, publication-quality graphs. Unlike Matplotlib (static images), Plotly graphs are rendered in JavaScript (D3.js stack) and allow zooming, panning, and hovering.

Key Features

1. Interactivity by Default
In a Jupyter Notebook or Web App (Streamlit/Dash), users can hover over points to see exact values.

2. High-Level API (Plotly Express)
Create complex charts in one line.

import plotly.express as px
df = px.data.iris()
fig = px.scatter(df, x="sepal_width", y="sepal_length", color="species")
fig.show()

3. Dashboards
Plotly is the rendering engine for Dash and Streamlit, making it the standard for Python Data Apps.

Chart Types
- Basic: Line, Bar, Scatter, Pie.
- Statistical: Box, Violin, Histogram, Heatmap.
- Scientific: 3D Surface, Contour, Log plots.
- Maps: Choropleth, Scatter Geo (using Mapbox).
- Financial: Candlestick charts.

Plotly vs Matplotlib
- Matplotlib: Better for static papers (PDF/EPS). Precise control.
- Plotly: Better for web, presentations, and exploration.

Rendering
It works entirely offline but creates HTML files or renders inline in Notebooks.