Saving figures in Data Analysis Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

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

Data Analysis Python

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

Bshow

Cplot

Dfigure

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 it as 'plot.png'.

2fill in blank

medium

Complete the code to save the figure with a resolution of 300 dots per inch (DPI).

Data Analysis Python

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

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

Aresolution

Bquality

Cdpi

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'quality' or 'resolution' instead of 'dpi'

Not specifying the dpi parameter at all

Using an invalid parameter name

The dpi parameter sets the resolution of the saved figure in dots per inch.

3fill in blank

hard

Fix the error in the code to save the figure as a PDF file named 'figure.pdf'.

Data Analysis Python

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

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

Asavefig

Bexport

Csave

Dshow

Attempts:

3 left

💡 Hint

Common Mistakes

Using plt.save() or plt.export() which are not valid functions

Using plt.show() instead of saving

Misspelling the function name

The correct function to save figures in matplotlib is savefig. Other options like save or export do not exist.

4fill in blank

hard

Fill both blanks to save the figure as a JPEG file with a transparent background.

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('image.jpg', [1]=[2])

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

Atransparent

BTrue

CFalse

Dalpha

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'alpha' instead of 'transparent' for background transparency

Setting transparent to False instead of True

Confusing parameter names

The transparent parameter set to True saves the figure background as transparent.

5fill in blank

hard

Fill all three blanks to save the figure as a high-quality SVG file with a tight bounding box.

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('diagram.svg', [1]=300, [2]='[3]')

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

Adpi

Bbbox_inches

Ctight

Dquality

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'quality' instead of 'dpi'

Not setting bbox_inches to 'tight'

Misspelling parameter names

Use dpi for resolution, bbox_inches set to 'tight' to reduce extra whitespace around the figure.

Practice

1. What is the main function used in Python's matplotlib to save a plot as an image file?

easy

A. plt.show()

B. plt.savefig()

C. plt.plot()

D. plt.save()

Solution

1. Step 1: Identify the function for saving plots

   The function plt.savefig() is designed to save the current figure to a file.

2. Step 2: Differentiate from other functions

   plt.show() displays the plot, plt.plot() creates the plot, and plt.save() does not exist.

3. Final Answer:

   plt.savefig() -> Option B

4. Quick Check:

   Save plot = plt.savefig() [OK]

Hint: Remember: save figure uses 'savefig' word [OK]

Common Mistakes:

• Confusing plt.show() with saving
• Using plt.save() which is not a valid function
• Thinking plt.plot() saves the figure

2. Which of the following is the correct syntax to save a plot as a PNG file with matplotlib?

easy

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

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

C. plt.savefig(plot.png)

D. plt.savefig('plot')

Solution

1. Step 1: Check the function name and argument type

   The correct function is plt.savefig() and it requires the filename as a string.

2. Step 2: Verify the filename format

   The filename must be a string with the extension, e.g., 'plot.png'. plt.savefig('plot.png') matches this exactly.

3. Final Answer:

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

4. Quick Check:

   Save with filename string = plt.savefig('plot.png') [OK]

Hint: Use quotes around filename with extension [OK]

Common Mistakes:

• Omitting quotes around filename
• Using plt.save() instead of plt.savefig()
• Missing file extension in filename

3. What will be the effect of this code snippet?

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

medium

A. Saves a PNG file named 'myplot.pdf' ignoring dpi and bbox_inches

B. Displays the plot on screen with 300 dpi resolution

C. Raises an error because dpi cannot be set for PDF files

D. Saves a PDF file named 'myplot.pdf' with high resolution and tight layout

Solution

1. Step 1: Understand plt.savefig parameters

   The code saves the plot as 'myplot.pdf' with dpi=300 for high resolution and bbox_inches='tight' to reduce whitespace.

2. Step 2: Confirm file format and parameters compatibility

   PDF supports dpi and bbox_inches parameters, so no error occurs and the file is saved correctly.

3. Final Answer:

   Saves a PDF file named 'myplot.pdf' with high resolution and tight layout -> Option D

4. Quick Check:

   Save PDF with dpi and tight bbox = correct [OK]

Hint: File extension sets format; dpi and bbox_inches improve quality [OK]

Common Mistakes:

• Thinking dpi is ignored for PDF
• Confusing save with display (plt.show())
• Assuming dpi causes error for PDF

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

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

medium

A. File extension '.png' is invalid

B. plt.plot() must be called after plt.savefig()

C. Missing quotes around filename 'myplot.png'

D. dpi parameter is required in plt.savefig()

Solution

1. Step 1: Check the argument to plt.savefig()

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

2. Step 2: Verify other parts of the code

   Calling plt.plot() before plt.savefig() is correct, dpi is optional, and '.png' is a valid extension.

3. Final Answer:

   Missing quotes around filename 'myplot.png' -> Option C

4. Quick Check:

   Filename must be string with quotes [OK]

Hint: Always put filename in quotes when saving [OK]

Common Mistakes:

• Forgetting quotes around filename
• Thinking dpi is mandatory
• Misordering plot and savefig calls

5. You want to save a plot as a high-quality PNG file with minimal white space around it. Which of the following code snippets achieves this correctly?

hard

A. plt.savefig('figure.png', dpi=600, bbox_inches='tight')

B. plt.savefig('figure.png', dpi=72, bbox_inches='standard')

C. plt.savefig('figure.png', dpi=600, bbox_inches='loose')

D. plt.savefig('figure.png', dpi='high', bbox_inches='tight')

Solution

1. Step 1: Understand dpi and bbox_inches parameters

   High dpi (e.g., 600) means better image quality. bbox_inches='tight' reduces extra white space.

2. Step 2: Evaluate each option

   plt.savefig('figure.png', dpi=600, bbox_inches='tight')

   uses dpi=600 and bbox_inches='tight' correctly.

   plt.savefig('figure.png', dpi=72, bbox_inches='standard')

   uses low dpi and invalid bbox_inches.

   plt.savefig('figure.png', dpi=600, bbox_inches='loose')

   uses bbox_inches='loose' which adds space.

   plt.savefig('figure.png', dpi='high', bbox_inches='tight')

   uses invalid dpi value 'high'.

3. Final Answer:

   plt.savefig('figure.png', dpi=600, bbox_inches='tight') -> Option A

4. Quick Check:

   High dpi + tight bbox = best quality [OK]

Hint: Use dpi=600 and bbox_inches='tight' for quality and layout [OK]

Common Mistakes:

• Using invalid dpi values like strings
• Choosing bbox_inches='loose' which adds whitespace
• Ignoring dpi leading to low-quality images