Line styles (solid, dashed, dotted) in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What line style is used in this plot code?

Look at the code below that draws a line using matplotlib. What line style will the line have?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([0, 1, 2], [0, 1, 0], linestyle='--')
plt.show()

A Dashed line

B Solid line

C Dotted line

D Dash-dot line

💡 Hint

The linestyle argument controls the pattern of the line.

The linestyle='--' means the line will be dashed. Solid is '-', dotted is ':', and dash-dot is '-.'.

❓ data_output

intermediate

How many lines are solid in this plot code?

The code below plots three lines with different line styles. How many lines will be solid?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [1, 2, 3], linestyle='-')
plt.plot([1, 2, 3], [3, 2, 1], linestyle=':')
plt.plot([1, 2, 3], [2, 2, 2], linestyle='--')
plt.show()

A 1

B 0

C 2

D 3

💡 Hint

Check the linestyle argument for each plot call.

Only the first plot uses linestyle='-', which is solid. The others are dotted ':' and dashed '--'.

❓ visualization

advanced

Identify the line style of the green line in this plot

This code plots three lines with colors and line styles. What is the line style of the green line?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([0, 1, 2], [2, 1, 0], color='red', linestyle=':')
plt.plot([0, 1, 2], [0, 1, 2], color='green', linestyle='-.')
plt.plot([0, 1, 2], [1, 1, 1], color='blue', linestyle='--')
plt.show()

A Dashed line

B Dash-dot line

C Solid line

D Dotted line

💡 Hint

Look at the linestyle argument for the green line.

The green line uses linestyle='-.', which is dash-dot style.

🧠 Conceptual

advanced

What error occurs with this invalid linestyle?

What error will this code produce when run?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([0, 1], [1, 0], linestyle='---')
plt.show()

A No error, plots a solid line

B SyntaxError: invalid syntax

C TypeError: linestyle must be a string

D ValueError: Unrecognized linestyle string

💡 Hint

Check if '---' is a valid linestyle in matplotlib.

Matplotlib does not recognize '---' as a valid linestyle and raises a ValueError.

🔧 Debug

expert

Why does this plot not show a dotted line?

The code below is intended to plot a dotted line but does not. Why?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([0, 1, 2], [0, 1, 0], linestyle='..')
plt.show()

A Because the plot function requires linewidth to show dotted lines

B Because '..' is interpreted as two dots, producing a dotted line

C Because '..' is not a valid linestyle, matplotlib defaults to solid line

D Because linestyle must be a tuple, not a string

💡 Hint

Check the valid linestyle strings in matplotlib.

Matplotlib does not recognize '..' as a valid linestyle, so it falls back to solid line.