Introduction to Matplotlib

What is Matplotlib?

Matplotlib is the core plotting library in Python.

• Flexible and powerful
• Works everywhere (scripts, notebooks)
• Backbone for many libraries (including Seaborn)

Matplotlib was started by John Hunter in 2002 to bring a MATLAB-like plotting interface to Python. It can export charts to almost every common format — PNG, SVG, PDF, and more — which is why it’s still the default choice for publication-quality figures, even with newer libraries around.

How a plot gets built

diagram From data to a rendered chart mermaid

  flowchart LR
  A["Your data"] --> B["Figure (the canvas)"]
  B --> C["Axes (one plotting area)"]
  C --> D["Artists (lines, bars, ticks, text)"]
  E["plt.plot() - quick pyplot API"] -.-> C
  F["fig, ax = plt.subplots() - OO API"] -.-> C

Matplotlib always builds a chart the same way: a Figure holds Axes, and you draw Artists onto the Axes.

Two common ways to plot

1) Pyplot (quick)

pyplot quick

import matplotlib.pyplot as plt
 
plt.plot([1, 2, 3], [3, 2, 5])
plt.title("Quick plot")
plt.show()

2) Object-oriented API (recommended)

OO API

import matplotlib.pyplot as plt
 
fig, ax = plt.subplots(figsize=(7, 4))
ax.plot([1, 2, 3], [3, 2, 5])
ax.set_title("OO plot")
ax.set_xlabel("x")
ax.set_ylabel("y")
plt.show()

Key terms

• Figure: the whole canvas
• Axes: the plotting area
• Artist: everything drawn on the figure

In this phase, we’ll focus on practical charts you need for analytics.

From the book

McKinney points out that matplotlib.pyplot functions like plt.plot() operate on “the active or most recently created” Axes — that’s why the quick pyplot style can feel magical (and confusing) once you have more than one subplot. The object-oriented API (fig, ax = plt.subplots()) avoids this ambiguity because you always call methods on a specific ax you’re holding a reference to.

Next

Continue to Anatomy of a Plot to see exactly how Figure, Axes, ticks, and labels fit together.

🧪 Try It Yourself

Exercise 1 – Object-oriented basics

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Exercise 2 – Labelling an Axes

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Exercise 3 – A grid of Axes

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