Why export quality matters in Matplotlib - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a simple line plot.

Matplotlib

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

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

Ashow

Bsavefig

Cplot

Dtitle

Attempts:

3 left

💡 Hint

Common Mistakes

Using savefig instead of show will save the plot but not display it.

Calling plot again instead of show will add more lines instead of displaying.

The show() function displays the plot on the screen.

2fill in blank

medium

Complete the code to save the plot as a PNG file.

Matplotlib

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

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

Ashow

Bplot

Csavefig

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using show instead of savefig will display but not save the plot.

Using close will close the plot without saving.

The savefig() function saves the current plot to a file.

3fill in blank

hard

Fix the error in saving the plot with high resolution.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [3, 2, 1])
plt.savefig('high_res_plot.png', dpi=[1])

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

Adpi

B300

C'300'

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Passing dpi as a string causes an error.

Using too low dpi results in poor image quality.

The dpi parameter expects an integer for resolution. 300 dpi is a common high-quality setting.

4fill in blank

hard

Fill both blanks to save a plot with a transparent background and tight layout.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [3, 2, 1])
plt.savefig('transparent_plot.png', [1]=True, [2]='tight')

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

Atransparent

Bdpi

Cbbox_inches

Dfacecolor

Attempts:

3 left

💡 Hint

Common Mistakes

Using facecolor instead of transparent for transparency.

Not using bbox_inches='tight' causes extra whitespace.

transparent=True makes the background see-through.
bbox_inches='tight' trims extra whitespace around the plot.

5fill in blank

hard

Fill all three blanks to save a plot with a custom size, high dpi, and no axis.

Matplotlib

import matplotlib.pyplot as plt
fig, ax = plt.subplots(figsize=([1], [2]))
ax.plot([1, 2, 3], [3, 2, 1])
ax.axis([3])
fig.savefig('custom_plot.png', dpi=300)

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

A8

B6

C'off'

D'on'

Attempts:

3 left

💡 Hint

Common Mistakes

Using strings instead of numbers for figsize.

Using 'on' instead of 'off' to hide axes.

figsize=(8, 6) sets the plot size in inches.
ax.axis('off') hides the axis lines and labels.
The plot is saved with 300 dpi for high quality.

Practice

1. Why is it important to set a higher dpi value when exporting a plot with plt.savefig()?

easy

A. It adds grid lines to the plot.

B. It changes the plot colors automatically.

C. It reduces the file size significantly.

D. It increases the resolution, making the image clearer and sharper.

Solution

1. Step 1: Understand what dpi means in image export

   DPI stands for dots per inch and controls the resolution of the saved image.

2. Step 2: Effect of higher dpi on image quality

   A higher dpi means more dots per inch, resulting in a clearer and sharper image when viewed or printed.

3. Final Answer:

   It increases the resolution, making the image clearer and sharper. -> Option D

4. Quick Check:

   Higher dpi = better image clarity [OK]

Hint: Higher dpi means sharper images when exporting plots [OK]

Common Mistakes:

• Thinking dpi changes colors
• Assuming dpi reduces file size
• Believing dpi adds plot elements

2. Which of the following is the correct syntax to save a plot with high quality using plt.savefig()?

easy

A. plt.savefig('plot.png', dpi=300, bbox_inches='tight')

B. plt.save('plot.png', quality=300)

C. plt.export('plot.png', dpi=300)

D. plt.savefig('plot.png', resolution=300)

Solution

1. Step 1: Recall the correct function name and parameters

   The correct function to save a plot is plt.savefig() with parameters like dpi and bbox_inches.

2. Step 2: Identify the correct syntax among options

   Only plt.savefig('plot.png', dpi=300, bbox_inches='tight') uses the correct function and valid parameters to improve export quality.

3. Final Answer:

   plt.savefig('plot.png', dpi=300, bbox_inches='tight') -> Option A

4. Quick Check:

   Correct function and parameters = plt.savefig('plot.png', dpi=300, bbox_inches='tight') [OK]

Hint: Use plt.savefig() with dpi and bbox_inches for quality [OK]

Common Mistakes:

• Using plt.save instead of plt.savefig
• Using wrong parameter names like resolution
• Missing bbox_inches='tight' to avoid cut-off

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

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('myplot.png', dpi=50)

medium

A. The saved image will be high resolution and very clear.

B. The saved image will be low resolution and appear blurry.

C. The plot will not be saved due to syntax error.

D. The saved image will have a transparent background.

Solution

1. Step 1: Understand dpi value effect on image quality

   A dpi of 50 is low, so the saved image will have low resolution.

2. Step 2: Predict the visual quality of the saved plot

   Low dpi causes the image to look blurry or pixelated when viewed at normal size.

3. Final Answer:

   The saved image will be low resolution and appear blurry. -> Option B

4. Quick Check:

   Low dpi = blurry image [OK]

Hint: Low dpi means blurry saved images [OK]

Common Mistakes:

• Assuming dpi=50 is high quality
• Expecting transparent background without setting it
• Thinking code has syntax errors

4. Identify the error in this code that tries to save a plot with high quality:

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

medium

A. The dpi value should be an integer, not a string.

B. The plot function is missing a title.

C. The file extension .png is not supported.

D. The savefig function requires a file path, not just a name.

Solution

1. Step 1: Check the dpi parameter type

   The dpi parameter must be an integer, but here it is passed as a string '300'.

2. Step 2: Understand the impact of wrong dpi type

   Passing dpi as a string causes a TypeError or unexpected behavior when saving the file.

3. Final Answer:

   The dpi value should be an integer, not a string. -> Option A

4. Quick Check:

   dpi must be int, not string [OK]

Hint: dpi must be a number, not text [OK]

Common Mistakes:

• Passing dpi as a string instead of integer
• Thinking file extension .png is invalid
• Believing savefig needs full file path always

5. You want to export a plot for a presentation slide. The plot has tight labels and legends that get cut off in the saved image. Which plt.savefig() option helps fix this issue while keeping high quality?

hard

A. Use dpi=50 and no other options.

B. Use transparent=True only.

C. Use bbox_inches='tight' with a high dpi value.

D. Use facecolor='white' only.

Solution

1. Step 1: Understand the problem of cut-off labels

   Labels and legends can be cut off if the bounding box is not adjusted when saving.

2. Step 2: Use bbox_inches='tight' to include all plot elements

   This option adjusts the bounding box to fit all parts of the plot, preventing cut-offs.

3. Step 3: Combine with high dpi for clear image

   Setting a high dpi ensures the saved image is sharp and professional for presentations.

4. Final Answer:

   Use bbox_inches='tight' with a high dpi value. -> Option C

5. Quick Check:

   bbox_inches='tight' + high dpi = clear, complete plot [OK]

Hint: bbox_inches='tight' fixes cut-off; dpi improves clarity [OK]

Common Mistakes:

• Ignoring bbox_inches causes cut-off
• Using low dpi reduces image quality
• Thinking transparent or facecolor fix cut-off