Plt.subplots with rows and columns in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the shape of the axes array?

Consider this code snippet using plt.subplots with 3 rows and 2 columns. What is the shape of the axes object?

Matplotlib

import matplotlib.pyplot as plt
fig, axes = plt.subplots(3, 2)
print(axes.shape)

A (2, 3)

B ()

C (6,)

D (3, 2)

💡 Hint

The axes is a 2D array matching rows and columns.

When you create subplots with 3 rows and 2 columns, axes is a 2D numpy array with shape (3, 2).

❓ data_output

intermediate

How many axes objects are created?

What is the total number of axes objects created by plt.subplots(4, 1)?

Matplotlib

import matplotlib.pyplot as plt
fig, axes = plt.subplots(4, 1)
print(len(axes))

A 4

B 1

C 5

D 0

💡 Hint

Number of axes equals rows times columns.

With 4 rows and 1 column, axes is a 1D array of length 4.

❓ visualization

advanced

Identify the subplot layout from the plot

You run this code to create subplots and plot data. Which layout matches the figure shown?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np
x = np.linspace(0, 10, 100)
fig, axes = plt.subplots(2, 3)
for i, ax in enumerate(axes.flat):
    ax.plot(x, np.sin(x + i))
plt.show()

A 2 rows and 3 columns

B 3 rows and 2 columns

C 1 row and 6 columns

D 6 rows and 1 column

💡 Hint

Check how many rows and columns are passed to plt.subplots.

The code creates 2 rows and 3 columns of subplots, so the figure shows 6 plots arranged in 2 rows and 3 columns.

🔧 Debug

advanced

Why does this code raise an error?

This code tries to plot on subplots but raises an error. What is the cause?

Matplotlib

import matplotlib.pyplot as plt
fig, axes = plt.subplots(2, 2)
axes[2].plot([1, 2, 3])
plt.show()

A ValueError because plot data is invalid

B TypeError because axes is not subscriptable

C IndexError because axes is a 2D array and index 2 is invalid

D No error, code runs fine

💡 Hint

Check the shape of axes and how indexing works.

The axes is a 2x2 array, so axes[2] is out of bounds. You must use two indices like axes[0, 1].

🚀 Application

expert

How to flatten axes for iteration?

You create subplots with 3 rows and 3 columns. You want to loop over all axes in one loop. Which code correctly flattens the axes array?

Matplotlib

import matplotlib.pyplot as plt
fig, axes = plt.subplots(3, 3)
# Which line below correctly flattens axes for iteration?

A

for ax in axes.flat:
    ax.plot([1, 2, 3])

B

for ax in axes.flatten():
    ax.plot([1, 2, 3])

C

for ax in axes.ravel():
    ax.plot([1, 2, 3])

D

for ax in axes:
    ax.plot([1, 2, 3])

💡 Hint

Check the methods available on numpy arrays for flattening.

The flatten() method returns a 1D copy of the array, allowing iteration over all axes.