Font properties customization in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the font size of the title in this plot?

Consider this matplotlib code that sets a title with a specific font size. What font size will the title text have?

Matplotlib

import matplotlib.pyplot as plt
plt.title('Sample Title', fontsize=18)
plt.plot([1, 2, 3], [4, 5, 6])
plt.show()

A 12

B 10

C 18

D 24

💡 Hint

Look at the fontsize argument inside plt.title.

The fontsize parameter in plt.title sets the font size of the title text. Here it is set to 18.

❓ data_output

intermediate

What font family is used in this text?

This code sets the font family of a label. What font family will the label text use?

Matplotlib

import matplotlib.pyplot as plt
plt.xlabel('X axis', fontfamily='serif')
plt.plot([1, 2], [3, 4])
plt.show()

A serif

B sans-serif

C cursive

D monospace

💡 Hint

Check the fontfamily argument in plt.xlabel.

The fontfamily parameter sets the font family. Here it is set to 'serif'.

❓ visualization

advanced

Which option produces a plot with bold and italic title text?

Given these four code snippets, which one will produce a plot with the title text both bold and italic?

A plt.title('Title', fontweight='bold', fontstyle='normal')

B plt.title('Title', fontweight='italic', fontstyle='bold')

C plt.title('Title', fontweight='normal', fontstyle='bold')

D plt.title('Title', fontweight='bold', fontstyle='italic')

💡 Hint

fontweight controls boldness, fontstyle controls italic style.

fontweight='bold' makes text bold, fontstyle='italic' makes text italic. Option D sets both correctly.

🔧 Debug

advanced

Why does this code raise an error?

This code tries to set font properties but raises an error. What is the cause?

Matplotlib

import matplotlib.pyplot as plt
plt.xlabel('X axis', fontweight=700)
plt.show()

A The code is correct and does not raise an error

B plt.xlabel does not accept fontweight argument

C fontweight should be set using plt.rcParams, not in xlabel

D fontweight must be a string like 'bold', not an integer

💡 Hint

fontweight accepts both strings (like 'bold') and integers (like 700).

The code is correct and does not raise an error. Matplotlib's fontweight accepts numeric values from 0-1000 (700 is bold) in addition to strings like 'bold'.

🚀 Application

expert

How to set different font properties for x and y axis labels in one plot?

You want the x-axis label to be italic and size 14, and the y-axis label to be bold and size 18. Which code snippet achieves this?

A

plt.xlabel('X axis', fontstyle='italic', fontweight='bold', fontsize=14)
plt.ylabel('Y axis', fontstyle='italic', fontweight='bold', fontsize=18)

B

plt.xlabel('X axis', fontstyle='italic', fontsize=14)
plt.ylabel('Y axis', fontweight='bold', fontsize=18)

C

plt.xlabel('X axis', fontweight='bold', fontsize=18)
plt.ylabel('Y axis', fontstyle='italic', fontsize=14)

D

plt.xlabel('X axis', fontsize=14)
plt.ylabel('Y axis', fontsize=18)

💡 Hint

Check the fontstyle and fontweight parameters for each label separately.

Option B correctly sets x label italic with size 14 and y label bold with size 18.

Practice

1. Which font property controls the thickness of the text in a matplotlib plot?

easy

A. family

B. size

C. weight

D. color

Solution

1. Step 1: Understand font properties

   Font properties include size, weight, family, style, and color.

2. Step 2: Identify the property for thickness

   The thickness or boldness of text is controlled by the 'weight' property.

3. Final Answer:

   weight -> Option C

4. Quick Check:

   Font thickness = weight [OK]

Hint: Thickness means weight in font properties [OK]

Common Mistakes:

• Confusing size with weight
• Thinking color controls thickness
• Mixing family with weight

2. Which of the following is the correct way to set the font size of a plot title to 16 using fontdict in matplotlib?

easy

A. plt.title('My Title', font={'fontsize':16})

B. plt.title('My Title', fontdict={'size':16})

C. plt.title('My Title', font={'size':16})

D. plt.title('My Title', fontdict={'fontsize':16})

Solution

1. Step 1: Recall fontdict usage

   In matplotlib, fontdict keys include 'size' for font size, not 'fontsize'.

2. Step 2: Check correct syntax

   Using fontdict={'size':16} correctly sets font size to 16.

3. Final Answer:

   plt.title('My Title', fontdict={'size':16}) -> Option B

4. Quick Check:

   fontdict uses 'size' key [OK]

Hint: Use 'size' key inside fontdict for font size [OK]

Common Mistakes:

• Using 'fontsize' instead of 'size'
• Using 'font' instead of 'fontdict'
• Wrong dictionary key names

3. What will be the font size of the x-axis label in the following code?

import matplotlib.pyplot as plt
plt.xlabel('X Axis', fontdict={'size':20, 'weight':'bold'})
plt.show()

medium

A. 20

B. Bold but default size

C. Default size (usually 10)

D. Error due to wrong fontdict

Solution

1. Step 1: Analyze fontdict in xlabel

   The fontdict sets 'size' to 20 and 'weight' to 'bold'.

2. Step 2: Understand effect on label

   The label will use size 20 and bold weight as specified.

3. Final Answer:

   20 -> Option A

4. Quick Check:

   fontdict size = 20 [OK]

Hint: fontdict size sets label font size directly [OK]

Common Mistakes:

• Assuming default size
• Ignoring weight property
• Thinking code causes error

4. Identify the error in this code snippet that tries to set the legend font to italic:

import matplotlib.pyplot as plt
plt.plot([1,2,3], label='Line')
plt.legend(prop={'style':'italic'})
plt.show()

medium

A. Missing plt.legend() call

B. No error, code runs fine

C. Incorrect label argument in plot

D. 'style' is not a valid font property key for legend prop

Solution

1. Step 1: Check font property keys for legend

   Valid keys include 'size', 'weight', 'family', 'style', and 'color'. 'style' is valid but must be a recognized value.

2. Step 2: Verify 'italic' usage

   'italic' is a valid style, so the key is correct. However, in matplotlib, 'style' should be set inside a FontProperties object or as a string, not directly in prop dict.

3. Step 3: Identify actual error

   The error is that 'prop' expects a FontProperties object or a dictionary with correct keys, but 'style' key is not always recognized directly in prop dict in some matplotlib versions.

4. Final Answer:

   'style' is not a valid font property key for legend prop -> Option D

5. Quick Check:

   Legend prop keys must be valid font properties [OK]

Hint: Use FontProperties for complex font styles in legend [OK]

Common Mistakes:

• Using wrong keys in prop dict
• Forgetting to import FontProperties
• Assuming all keys work directly

5. You want to create a plot with a title that uses a custom font family 'Comic Sans MS', size 18, bold weight, and blue color. Which code snippet correctly applies all these font properties?

hard

A. plt.title('My Plot', fontdict={'family':'Comic Sans MS', 'size':18, 'weight':'bold', 'color':'blue'})

B. plt.title('My Plot', fontdict={'fontfamily':'Comic Sans MS', 'fontsize':18, 'fontweight':'bold', 'fontcolor':'blue'})

C. plt.title('My Plot', font={'family':'Comic Sans MS', 'size':18, 'weight':'bold', 'color':'blue'})

D. plt.title('My Plot', fontdict={'family':'Comic Sans MS', 'fontsize':18, 'weight':'bold', 'color':'blue'})

Solution

1. Step 1: Check correct fontdict keys

   Valid keys are 'family', 'size', 'weight', and 'color'. 'fontsize' and 'fontweight' are incorrect keys here.

2. Step 2: Verify values and syntax

   plt.title('My Plot', fontdict={'family':'Comic Sans MS', 'size':18, 'weight':'bold', 'color':'blue'}) uses correct keys and values for family, size, weight, and color.

3. Final Answer:

   plt.title('My Plot', fontdict={'family':'Comic Sans MS', 'size':18, 'weight':'bold', 'color':'blue'}) -> Option A

4. Quick Check:

   Use 'family', 'size', 'weight', 'color' keys in fontdict [OK]

Hint: Use standard keys: family, size, weight, color in fontdict [OK]

Common Mistakes:

• Using 'fontsize' instead of 'size'
• Using 'fontcolor' instead of 'color'
• Passing fontdict as 'font'