Font properties customization in Matplotlib - Step-by-Step Execution

Concept Flow - Font properties customization

Start plot setup

↓

Define font properties

↓

Apply font properties to text

↓

Render plot with customized fonts

↓

Display or save plot

↓

End

This flow shows how to define font properties, apply them to plot text elements, and then render the plot with customized fonts.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
from matplotlib.font_manager import FontProperties

font = FontProperties(family='serif', style='italic', size=14)
plt.title('Hello', fontproperties=font)
plt.show()

This code sets a serif italic font of size 14 for the plot title and displays the plot.

Execution Table

Step	Action	FontProperties State	Text Element	Effect
1	Import matplotlib and FontProperties	No font properties defined	None	No text yet
2	Create FontProperties with family='serif', style='italic', size=14	family='serif', style='italic', size=14	None	Font properties ready
3	Set plot title with fontproperties=font	family='serif', style='italic', size=14	Title text 'Hello'	Title uses defined font
4	Call plt.show()	family='serif', style='italic', size=14	Title text 'Hello'	Plot window opens showing title with customized font
5	End of execution	family='serif', style='italic', size=14	Title text 'Hello'	Execution stops after plot display

💡 Plot displayed with title using customized font properties; execution ends.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
font	None	FontProperties(family='serif', style='italic', size=14)	Same	Same
title text	None	None	'Hello' with fontproperties=font	'Hello' with fontproperties=font

Key Moments - 2 Insights

Why do we need to create a FontProperties object before applying it?

Creating a FontProperties object lets us specify font details once and reuse them. In the execution_table step 2, the font object is created with desired settings, which is then applied to the title in step 3.

What happens if we don't pass fontproperties to the title?

If fontproperties is not passed (see execution_table step 3), the title uses default font settings. The customized font won't apply, so the title looks standard.

Visual Quiz - 3 Questions

Look at the execution_table at step 3. What font style is applied to the title text?

A Italic

B Bold

C Normal

D Underline

💡 Hint

Check the FontProperties state column at step 3 showing style='italic'.

At which step does the plot window open showing the customized font?

A Step 3

B Step 4

C Step 2

D Step 5

💡 Hint

Look at the Effect column; plot display happens at step 4.

If we change the font size to 20 in the FontProperties, how would the variable 'font' change after step 2?

A FontProperties with size=14

B FontProperties with size=10

C FontProperties with size=20

D No change

💡 Hint

Variable tracker shows font size set at creation (step 2). Changing size changes this value.

Concept Snapshot

Font Properties Customization in matplotlib:
- Import FontProperties from matplotlib.font_manager
- Create a FontProperties object with family, style, size
- Pass fontproperties=font to text elements like title, xlabel
- Plot renders text with specified font styles
- Useful for consistent font styling across plots

Full Transcript

This visual execution shows how to customize font properties in matplotlib plots. First, we import necessary modules. Then, we create a FontProperties object specifying font family, style, and size. Next, we apply this font object to a plot title. Finally, we display the plot, which shows the title in the customized font. Variables like 'font' hold the font settings, and the title text uses these settings when drawn. Key points include creating the font object before use and passing it explicitly to text elements to see the effect.

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'