Basic plt.plot usage in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What does this matplotlib code plot?

Consider the following Python code using matplotlib. What kind of plot will it produce?

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3, 4]
y = [10, 20, 25, 30]
plt.plot(x, y)
plt.show()

A A line graph connecting points (1,10), (2,20), (3,25), (4,30)

B A scatter plot with points at (1,10), (2,20), (3,25), (4,30)

C A bar chart with bars at x=1,2,3,4 with heights 10,20,25,30

D An empty plot with no data shown

💡 Hint

plt.plot by default draws lines connecting points.

The plt.plot function draws a line graph connecting the points given by x and y lists.

❓ data_output

intermediate

What is the y-value of the third point plotted?

Given this code snippet, what is the y-value of the third point plotted?

Matplotlib

import matplotlib.pyplot as plt
x = [0, 1, 2, 3]
y = [5, 15, 25, 35]
plt.plot(x, y)
plt.show()

A 25

B 15

C 35

D 5

💡 Hint

Indexing starts at 0, so the third point is at index 2.

The third point corresponds to index 2 in the y list, which is 25.

❓ visualization

advanced

Which option produces a red dashed line plot?

Which code snippet will produce a red dashed line connecting points (1,2), (2,4), (3,6)?

A plt.plot([1,2,3], [2,4,6], 'g-')

B plt.plot([1,2,3], [2,4,6], color='blue', linestyle='--')

C plt.plot([1,2,3], [2,4,6], 'r--')

D plt.plot([1,2,3], [2,4,6], linestyle=':')

💡 Hint

The format string 'r--' means red dashed line.

The 'r--' format string sets the line color to red and line style to dashed.

🔧 Debug

advanced

What error does this code raise?

What error will this code raise when executed?

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [4, 5]
plt.plot(x, y)
plt.show()

A TypeError: unsupported operand type(s)

B ValueError: x and y must have same first dimension

C IndexError: list index out of range

D No error, plot will display correctly

💡 Hint

x and y lists must be the same length for plt.plot.

The x list has length 3 but y has length 2, causing a ValueError.

🚀 Application

expert

How many lines will this code plot?

Given this code, how many separate lines will appear in the plot?

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3]
y1 = [2, 4, 6]
y2 = [1, 3, 5]
plt.plot(x, y1, x, y2)
plt.show()

A 3

B 1

C 0

D 2

💡 Hint

plt.plot can take multiple x,y pairs to plot multiple lines.

The code plots two lines: one for (x,y1) and one for (x,y2).