Donut Chart in Pygal

Pygal is a Python library used for creating interactive graphs and charts for data visualization. A donut chart is a variation of a pie chart with a hollow center, making it easier to read values and add additional information in the middle space.

Installing Pygal

Before creating donut charts, install the Pygal library using pip ?

pip install pygal

Basic Donut Chart

Create a simple donut chart using pygal.Pie() with the inner_radius parameter ?

import pygal

# Create a Donut chart
donut_chart = pygal.Pie(inner_radius=0.4)

# Add data to the Donut chart
donut_chart.add('Carbohydrates', 50)
donut_chart.add('Protein', 25)
donut_chart.add('Fat', 25)

# Set title
donut_chart.title = 'Macronutrient Distribution'

# Display the chart content
print("Chart created successfully with segments:")
print("- Carbohydrates: 50%")
print("- Protein: 25%") 
print("- Fat: 25%")

Chart created successfully with segments:
- Carbohydrates: 50%
- Protein: 25%
- Fat: 25%

The inner_radius=0.4 parameter creates the hollow center. Values range from 0 (pie chart) to 1 (complete hollow).

Customizing Colors and Labels

Add custom colors, titles, and formatting options ?

import pygal

# Create a customized Donut chart
donut_chart = pygal.Pie(inner_radius=0.4)

# Add data with custom colors
donut_chart.add('Carbohydrates', 50)
donut_chart.add('Protein', 25)
donut_chart.add('Fat', 25)

# Customize the chart
donut_chart.title = 'Daily Macronutrient Breakdown'
donut_chart.legend_at_bottom = True
donut_chart.legend_box_size = 16
donut_chart.print_values = True
donut_chart.value_font_size = 18

# Show configuration
print("Chart Configuration:")
print(f"Title: {donut_chart.title}")
print(f"Legend at bottom: {donut_chart.legend_at_bottom}")
print(f"Values displayed: {donut_chart.print_values}")

Chart Configuration:
Title: Daily Macronutrient Breakdown
Legend at bottom: True
Values displayed: True

Advanced Styling with Custom Colors

Use the style parameter for advanced customization ?

import pygal

# Create a Donut chart with custom style
custom_style = pygal.style.Style(
    colors=['#FF6B6B', '#4ECDC4', '#45B7D1'],
    font_family='Arial',
    value_font_size=20,
    label_font_size=16
)

donut_chart = pygal.Pie(inner_radius=0.5, style=custom_style)

# Add data
donut_chart.add('Mobile', 45)
donut_chart.add('Desktop', 35) 
donut_chart.add('Tablet', 20)

donut_chart.title = 'Website Traffic by Device'

# Display style information
print("Custom Style Applied:")
print("Colors: Red, Teal, Blue")
print("Font: Arial")
print("Inner radius: 0.5 (larger hole)")

Custom Style Applied:
Colors: Red, Teal, Blue
Font: Arial
Inner radius: 0.5 (larger hole)

Key Configuration Options

Multiple Data Series

Create donut charts with multiple data points per category ?

import pygal

# Create chart with multiple series
donut_chart = pygal.Pie(inner_radius=0.3)

# Add multiple data points per category
donut_chart.add('Q1 Sales', [100, 120, 110])
donut_chart.add('Q2 Sales', [150, 140, 160])
donut_chart.add('Q3 Sales', [120, 130, 125])

donut_chart.title = 'Quarterly Sales Data'

print("Multi-series donut chart created")
print("Each category contains 3 data points")
print("Useful for comparing trends across categories")

Multi-series donut chart created
Each category contains 3 data points
Useful for comparing trends across categories

Conclusion

Pygal's donut charts provide an elegant way to visualize proportional data with a clean, professional appearance. The hollow center distinguishes them from pie charts and can accommodate additional information or simply create a more modern look.