How Matplotlib renders figures - Practice Exercises

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Matplotlib code?

Consider the following Python code using Matplotlib. What will be the output when this code runs?

Matplotlib

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
ax.plot([1, 2, 3], [4, 5, 6])
print(type(fig))

A <class 'matplotlib.figure.Figure'>

B <class 'matplotlib.axes.Axes'>

C <class 'list'>

D <class 'tuple'>

💡 Hint

Remember, plt.subplots() returns a figure and axes object. The variable fig stores the figure.

The fig variable holds the Figure object, so printing its type shows matplotlib.figure.Figure.

❓ data_output

intermediate

How many axes are created by this code?

Look at this code snippet. How many axes objects are created?

Matplotlib

import matplotlib.pyplot as plt
fig, axs = plt.subplots(2, 2)
print(len(axs.flatten()))

A 4

B 0

C 1

D 2

💡 Hint

Think about the grid size in plt.subplots(2, 2).

The code creates a 2x2 grid of axes, so there are 4 axes in total.

❓ visualization

advanced

Which option shows the correct figure rendering order?

Matplotlib renders figure elements in a specific order. Which option correctly orders these steps?

• 1. Drawing axes
• 2. Creating figure canvas
• 3. Rendering figure to screen
• 4. Drawing figure background

A 1, 2, 4, 3

B 2, 4, 1, 3

C 2, 1, 4, 3

D 4, 2, 1, 3

💡 Hint

Think about what happens first: setting up the canvas, then background, then axes, then showing.

Matplotlib first creates the canvas, then draws the figure background, then draws axes, and finally renders the figure to the screen.

🔧 Debug

advanced

What error does this code raise?

What error will this Matplotlib code produce?

Matplotlib

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

A AttributeError: 'AxesSubplot' object has no attribute 'plot'

B TypeError: 'int' object is not iterable

C ValueError: x and y must have same first dimension

D No error, plot displays correctly

💡 Hint

Check the lengths of the x and y data lists passed to plot().

The x list has 3 elements but y has only 2, causing a ValueError about dimension mismatch.

🚀 Application

expert

What is the final size of the saved figure in pixels?

This code saves a figure. What is the size in pixels of the saved image?

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(figsize=(4, 3), dpi=150)
fig.savefig('test.png')

A 450 x 600 pixels

B 4 x 3 pixels

C 150 x 150 pixels

D 600 x 450 pixels

💡 Hint

Multiply figure size in inches by dpi to get pixels.

Width in pixels = 4 inches * 150 dpi = 600 pixels; height = 3 inches * 150 dpi = 450 pixels.