Saving figures to files in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to save the figure as a PNG file named 'plot.png'.

Matplotlib

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

Drag options to blanks, or click blank then click option'

Asavefig

Bfigure

Cshow

Dplot

Attempts:

3 left

💡 Hint

Common Mistakes

Using plt.show() instead of plt.savefig()

Trying to save the figure before plotting

Misspelling the function name

The savefig function saves the current figure to a file. Here, it saves as 'plot.png'.

2fill in blank

medium

Complete the code to save the figure as a PDF file named 'chart.pdf'.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([10, 20, 30], [1, 4, 9])
plt.[1]('chart.pdf')

Drag options to blanks, or click blank then click option'

Ashow

Bsavefig

Cclose

Dfigure

Attempts:

3 left

💡 Hint

Common Mistakes

Using plt.show() instead of plt.savefig()

Not specifying the file name with extension

Trying to save before plotting

Use savefig to save the figure to a file. The file extension '.pdf' saves it as a PDF.

3fill in blank

hard

Fix the error in the code to save the figure as 'output.jpg'.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [3, 2, 1])
plt.[1]('output.jpg')

Drag options to blanks, or click blank then click option'

Asavefig

Bsave

Csave_figure

Dsave_plot

Attempts:

3 left

💡 Hint

Common Mistakes

Using plt.save() which does not exist

Misspelling savefig

Not calling the function on plt

The correct function to save a figure is savefig, not save.

4fill in blank

hard

Fill both blanks to save the figure as a high-resolution PNG file named 'highres.png' with 300 dpi.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([5, 10, 15], [2, 4, 6])
plt.[1]('highres.png', [2]=300)

Drag options to blanks, or click blank then click option'

Asavefig

Bdpi

Cquality

Dresolution

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter name like 'quality' or 'resolution'

Not specifying dpi for high resolution

Using plt.show() instead of plt.savefig()

Use savefig to save the figure. The dpi parameter sets the resolution in dots per inch.

5fill in blank

hard

Fill all three blanks to save the figure as 'custom.svg' with transparent background and tight bounding box.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([7, 8, 9], [1, 3, 5])
plt.[1]('custom.svg', [2]=True, [3]='tight')

Drag options to blanks, or click blank then click option'

Asavefig

Btransparent

Cbbox_inches

Dshow

Attempts:

3 left

💡 Hint

Common Mistakes

Using plt.show() instead of plt.savefig()

Misspelling parameter names

Not using bbox_inches to reduce whitespace

Use savefig to save the figure. The transparent=True makes the background transparent. The bbox_inches='tight' trims extra whitespace.

Practice

1. What does the plt.savefig() function do in matplotlib?

easy

A. It saves the current figure to a file on your computer.

B. It displays the figure on the screen.

C. It clears the current figure.

D. It creates a new figure window.

Solution

1. Step 1: Understand the purpose of plt.savefig()

   This function is used to save the current plot or figure to a file, such as PNG or PDF.

2. Step 2: Differentiate from display functions

   Functions like plt.show() display the figure, but plt.savefig() writes it to disk.

3. Final Answer:

   It saves the current figure to a file on your computer. -> Option A

4. Quick Check:

   plt.savefig() saves figure [OK]

Hint: Remember: savefig saves, show displays [OK]

Common Mistakes:

• Confusing plt.savefig() with plt.show()
• Thinking savefig displays the plot
• Assuming savefig clears the figure

2. Which of the following is the correct syntax to save a figure as a PNG file named 'plot.png'?

easy

A. plt.save('plot.png')

B. plt.savefig('plot.png')

C. plt.savefig(plot.png)

D. plt.save_figure('plot.png')

Solution

1. Step 1: Recall the correct function name

   The function to save figures is plt.savefig(), not plt.save() or others.

2. Step 2: Check the argument format

   The filename must be a string, so it should be in quotes: 'plot.png'.

3. Final Answer:

   plt.savefig('plot.png') -> Option B

4. Quick Check:

   Correct function and string filename [OK]

Hint: Use plt.savefig('filename.ext') with quotes [OK]

Common Mistakes:

• Missing quotes around filename
• Using incorrect function name
• Passing filename without quotes

3. What will happen if you run this code?

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('myplot.pdf', dpi=300)
plt.close()

medium

A. The plot is shown on screen but not saved.

B. An error occurs because dpi is not allowed with PDF files.

C. A PDF file named 'myplot.pdf' is saved with high resolution.

D. The file 'myplot.pdf' is saved but with default dpi 72.

Solution

1. Step 1: Understand plt.savefig() with dpi parameter

   Setting dpi=300 increases the resolution of the saved image, including PDF files.

2. Step 2: Confirm file saving and closing

   The code saves the plot as 'myplot.pdf' with dpi 300, then closes the figure to free memory.

3. Final Answer:

   A PDF file named 'myplot.pdf' is saved with high resolution. -> Option C

4. Quick Check:

   savefig with dpi=300 saves high-res PDF [OK]

Hint: dpi controls resolution; works with PDF too [OK]

Common Mistakes:

• Thinking dpi is ignored for PDF
• Expecting plot to display automatically
• Confusing plt.close() with plt.show()

4. Identify the error in this code snippet that tries to save a figure:

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

medium

A. The file extension '.png' is invalid.

B. plt.show() must come before plt.savefig().

C. plt.plot() is missing a figure creation step.

D. The filename is not enclosed in quotes.

Solution

1. Step 1: Check the filename argument in plt.savefig()

   The filename must be a string, so it needs quotes: 'myplot.png'.

2. Step 2: Verify order of plt.show() and plt.savefig()

   Calling plt.savefig() before plt.show() is correct and common practice.

3. Final Answer:

   The filename is not enclosed in quotes. -> Option D

4. Quick Check:

   Filename must be a string in quotes [OK]

Hint: Always put filename in quotes in savefig() [OK]

Common Mistakes:

• Omitting quotes around filename
• Thinking plt.show() must come first
• Assuming file extension is wrong

5. You want to save a plot tightly cropped around the content to avoid extra white space. Which plt.savefig() parameter helps achieve this?

hard

A. bbox_inches='tight'

B. format='png'

C. transparent=True

D. dpi=300

Solution

1. Step 1: Understand the role of bbox_inches

   The parameter bbox_inches='tight' trims the saved figure to fit the content closely, removing extra margins.

2. Step 2: Differentiate from other parameters

   dpi controls resolution, transparent controls background, and format sets file type, none affect cropping.

3. Final Answer:

   bbox_inches='tight' -> Option A

4. Quick Check:

   Use bbox_inches='tight' to crop figure [OK]

Hint: Use bbox_inches='tight' to crop saved figure [OK]

Common Mistakes:

• Confusing dpi with cropping
• Using transparent instead of bbox_inches
• Setting format does not crop figure