Font size guidelines in Matplotlib - Step-by-Step Execution

Concept Flow - Font size guidelines

Start Plot

↓

Set Font Size

↓

Apply Font Size to Title

↓

Apply Font Size to Axis Labels

↓

Apply Font Size to Tick Labels

↓

Render Plot with Fonts

↓

End

The flow shows how font sizes are set step-by-step for different parts of a matplotlib plot before rendering.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.title('My Plot', fontsize=16)
plt.xlabel('X Axis', fontsize=12)
plt.ylabel('Y Axis', fontsize=12)
plt.tick_params(labelsize=10)
plt.show()

This code creates a simple line plot and sets font sizes for the title, axis labels, and tick labels.

Execution Table

Step	Action	Font Size Set	Target Element	Effect
1	Create plot	Default	Plot area	Plot initialized with default font sizes
2	Set title font size	16	Title	Title font size set to 16 points
3	Set x-axis label font size	12	X-axis label	X-axis label font size set to 12 points
4	Set y-axis label font size	12	Y-axis label	Y-axis label font size set to 12 points
5	Set tick label font size	10	Tick labels	Tick labels font size set to 10 points
6	Render plot	Applied	All text elements	Plot displayed with specified font sizes

💡 Plot rendered with all font sizes applied as specified.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	Final
title_fontsize	Default (varies)	16	16	16	16	16
xlabel_fontsize	Default (varies)	Default	12	12	12	12
ylabel_fontsize	Default (varies)	Default	Default	12	12	12
tick_labelsize	Default (varies)	Default	Default	Default	10	10

Key Moments - 2 Insights

Why do we set font sizes separately for title, labels, and ticks?

Each text element has its own font size property, so setting them separately (see execution_table steps 2-5) allows precise control over appearance.

What happens if we don't set tick label font size explicitly?

Tick labels keep the default size, which may be too small or large compared to other text (see variable_tracker tick_labelsize before step 5).

Visual Quiz - 3 Questions

Look at the execution table, what font size is set for the plot title at step 2?

A 12

B 10

C 16

D Default

💡 Hint

Check the 'Font Size Set' column at step 2 in the execution_table.

At which step are the tick label font sizes set?

A Step 5

B Step 3

C Step 4

D Step 6

💡 Hint

Look for 'Set tick label font size' in the 'Action' column of execution_table.

If we remove the line setting xlabel font size, what happens to xlabel_fontsize in variable_tracker after step 3?

A It becomes 16

B It stays at default

C It becomes 10

D It becomes 12

💡 Hint

Check how xlabel_fontsize changes after step 3 in variable_tracker.

Concept Snapshot

matplotlib font size guidelines:
- Use 'fontsize' parameter to set size for title, xlabel, ylabel.
- Use 'tick_params(labelsize=...)' to set tick label size.
- Set sizes separately for clear control.
- Sizes are in points (pt).
- Apply before plt.show() to see effect.

Full Transcript

This visual execution shows how to set font sizes in matplotlib plots. We start by creating a plot, then set font sizes for the title, x-axis label, y-axis label, and tick labels step-by-step. Each step updates the font size of a specific text element. The variable tracker shows how font size values change after each step. Key moments clarify why separate settings are needed and what happens if some are omitted. The quiz tests understanding of font size assignments at different steps. This helps beginners see exactly how font sizes affect plot text elements.

Practice

1. Why is it important to set font sizes in a matplotlib chart?

easy

A. To increase the chart size

B. To change the chart colors

C. To add more data points

D. To make the chart text clear and easy to read

Solution

1. Step 1: Understand the role of font size in charts

   Font size controls how big or small the text appears on the chart, affecting readability.

2. Step 2: Connect font size to clarity

   Clear and readable text helps viewers understand the chart easily without straining their eyes.

3. Final Answer:

   To make the chart text clear and easy to read -> Option D

4. Quick Check:

   Font size improves readability = D [OK]

Hint: Font size controls text clarity on charts [OK]

Common Mistakes:

• Confusing font size with chart colors
• Thinking font size changes data points
• Assuming font size changes chart dimensions

2. Which of the following is the correct way to set the font size of the title in matplotlib?

easy

A. plt.title('My Chart', fontsize=14)

B. plt.title('My Chart', size=14px)

C. plt.title('My Chart', font=14)

D. plt.title('My Chart', font_size='large')

Solution

1. Step 1: Recall matplotlib title font size syntax

   The correct parameter to set font size is fontsize with an integer value.

2. Step 2: Check each option for correct syntax

   plt.title('My Chart', fontsize=14) uses fontsize=14, which is correct. Others use invalid parameters or units.

3. Final Answer:

   plt.title('My Chart', fontsize=14) -> Option A

4. Quick Check:

   Use fontsize=number for title font size = C [OK]

Hint: Use fontsize=number to set font size in matplotlib [OK]

Common Mistakes:

• Using size=14px instead of fontsize=14
• Using font_size or font parameters incorrectly
• Adding units like 'px' which matplotlib does not accept

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

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.xlabel('X Axis', fontsize=16)
plt.show()

medium

A. 16 points

B. Default font size (usually 10)

C. 12 points

D. No label will appear

Solution

1. Step 1: Identify the font size parameter in xlabel

   The code uses fontsize=16 in plt.xlabel, which sets the label font size to 16 points.

2. Step 2: Understand matplotlib default behavior

   Since fontsize is explicitly set, it overrides the default size (usually 10).

3. Final Answer:

   16 points -> Option A

4. Quick Check:

   Explicit fontsize=16 sets label size = A [OK]

Hint: Check fontsize parameter value to find label size [OK]

Common Mistakes:

• Assuming default size when fontsize is set
• Confusing label font size with tick font size
• Thinking label won't show without extra commands

4. Identify the error in this code that tries to set font sizes for ticks:

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.tick_params(axis='x', labelsize=14)
plt.yticks(fontsize='large')
plt.show()

medium

A. plt.tick_params syntax is wrong

B. fontsize='large' is invalid for plt.yticks

C. plt.plot syntax is wrong

D. plt.show() is missing

Solution

1. Step 1: Check syntax for tick font sizes

   Matplotlib expects labelsize=int in tick_params, not fontsize='large' in plt.yticks.

2. Step 2: Identify which line has the error

   plt.yticks(fontsize='large') is invalid and will cause an error.

3. Final Answer:

   fontsize='large' is invalid for plt.yticks -> Option B

4. Quick Check:

   Use tick_params(labelsize=int) for ticks [OK]

Hint: Use plt.tick_params(labelsize=number) for tick font sizes [OK]

Common Mistakes:

• Using string values like 'large' for tick fontsize
• Thinking plt.tick_params syntax is wrong
• Ignoring error messages about parameter types

5. You want to create a plot with a large title, medium axis labels, and small tick labels for clarity. Which font size settings follow good font size guidelines?

hard

A. Title fontsize=14, labels fontsize=14, ticks fontsize=14

B. Title fontsize=8, labels fontsize=20, ticks fontsize=14

C. Title fontsize=20, labels fontsize=14, ticks fontsize=8

D. Title fontsize=8, labels fontsize=8, ticks fontsize=8

Solution

1. Step 1: Understand font size roles for clarity

   Title should be largest to stand out, axis labels medium for readability, ticks smallest to avoid clutter.

2. Step 2: Match options to guideline

   Title fontsize=20, labels fontsize=14, ticks fontsize=8 matches this pattern: 20 (large), 14 (medium), 8 (small). Others do not follow this order.

3. Final Answer:

   Title fontsize=20, labels fontsize=14, ticks fontsize=8 -> Option C

4. Quick Check:

   Large title, medium labels, small ticks = A [OK]

Hint: Title > labels > ticks in font size for clarity [OK]

Common Mistakes:

• Making tick labels larger than title
• Using same font size for all text elements
• Choosing too small font sizes causing unreadable text