How Matplotlib renders figures

Introduction

Matplotlib draws pictures (figures) so you can see your data as graphs. Understanding how it creates these pictures helps you make better charts.

You want to show data trends with a line or bar chart.

You need to save a graph as an image file to share.

You want to customize how your chart looks before showing it.

You want to update a chart dynamically in a program.

You want to understand why your chart looks a certain way.

Syntax

Matplotlib

import matplotlib.pyplot as plt

fig, ax = plt.subplots()
ax.plot([1, 2, 3], [4, 5, 6])
plt.show()

fig is the whole picture (figure).

ax is the area where the data is drawn (axes).

Examples

This creates a figure and adds one plot area manually.

Matplotlib

import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot([1, 2, 3], [4, 5, 6])
plt.show()

This creates two stacked plots in one figure.

Matplotlib

import matplotlib.pyplot as plt

fig, ax = plt.subplots(2, 1)
ax[0].plot([1, 2, 3], [4, 5, 6])
ax[1].bar([1, 2, 3], [6, 5, 4])
plt.show()

Sample Program

This code creates a figure with one plot area, draws a line graph, adds labels and a title, then shows the figure window.

Matplotlib

import matplotlib.pyplot as plt

# Create a figure and axes
fig, ax = plt.subplots()

# Plot some data
ax.plot([0, 1, 2, 3], [10, 20, 25, 30], label='Line')

# Add title and labels
ax.set_title('Simple Line Plot')
ax.set_xlabel('X axis')
ax.set_ylabel('Y axis')

# Show legend
ax.legend()

# Display the figure
plt.show()

Important Notes

Matplotlib first creates a Figure object which is like a blank canvas.

Inside the figure, Axes objects are created where data is drawn.

When you call plt.show(), Matplotlib renders the figure on your screen.

Summary

Matplotlib draws figures by creating a Figure and one or more Axes inside it.

You add data to Axes, then call plt.show() to see the graph.

Understanding this helps you control how your charts look and behave.