Saving figures in Data Analysis Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output file format?

Consider this Python code that saves a plot:

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('myplot.png')
print('File saved')

What is the format of the saved file?

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('myplot.png')
print('File saved')

A PNG image file

B JPEG image file

C SVG vector graphic

D PDF document

💡 Hint

Look at the file extension in the filename.

The file extension '.png' tells matplotlib to save the figure as a PNG image file.

❓ data_output

intermediate

How many files are saved?

This code saves multiple figures:

import matplotlib.pyplot as plt
for i in range(3):
    plt.figure()
    plt.plot([1, 2], [i, i+1])
    plt.savefig(f'plot_{i}.png')

How many image files are created after running this code?

Data Analysis Python

import matplotlib.pyplot as plt
for i in range(3):
    plt.figure()
    plt.plot([1, 2], [i, i+1])
    plt.savefig(f'plot_{i}.png')

A 0 files

B 1 file

C 3 files

D 2 files

💡 Hint

Count how many times savefig is called.

The loop runs 3 times, saving one file each time, so 3 files are created.

🔧 Debug

advanced

Why is the saved figure blank?

Look at this code:

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('figure.png')
plt.show()

After running it, the saved file 'figure.png' is blank. Why?

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('figure.png')
plt.show()

A The savefig filename is invalid

B The figure is saved after showing, so it is blank

C The plot command is missing

D The figure is saved before showing, so it is blank

💡 Hint

Think about when the figure content is finalized.

Calling plt.show() clears the figure. Saving before showing saves the correct image. But if the figure is blank, it means the figure was saved after it was cleared by show.

❓ visualization

advanced

Which option saves a figure with transparent background?

You want to save a plot with a transparent background. Which code does this?

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])

A plt.savefig('plot.png', transparent=True)

B plt.savefig('plot.png', bg='transparent')

C plt.savefig('plot.png', alpha=0.5)

D plt.savefig('plot.png', transparent=False)

💡 Hint

Check the savefig parameters for transparency.

The transparent=True argument saves the figure background as transparent.

🚀 Application

expert

How to save a high-resolution figure?

You want to save a figure with higher quality for printing. Which option correctly sets the resolution to 300 dots per inch (DPI)?

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])

A plt.savefig('highres.png', dpi='300dpi')

B plt.savefig('highres.png', resolution=300)

C plt.savefig('highres.png', quality=300)

D plt.savefig('highres.png', dpi=300)

💡 Hint

Look for the correct parameter name and type for DPI.

The dpi parameter sets the resolution as an integer. Other parameters like resolution or quality are invalid.