Gauge Chart in pygal

Gauge charts are a type of chart used to represent a value or a range of values in a circular format. These charts are similar to speedometer gauges in cars, where a needle points to a particular value on the gauge. Gauge charts can be useful for visualizing data related to performance indicators, such as completion rates or progress towards a goal. In this tutorial, we will explore how to create gauge charts using the pygal library in Python.

Installation

To use pygal, you first need to install it using Package Manager PIP ?

pip install pygal

Basic Syntax

To create a basic gauge chart using pygal, you can use the following syntax ?

import pygal

# create a gauge chart
gauge_chart = pygal.Gauge()

# add data to the chart
gauge_chart.add('Label', value)

# render the chart
gauge_chart.render_to_file('chart.svg')

Simple Gauge Chart Example

Here is a simple example that creates a gauge chart to represent completion percentage ?

import pygal

# create a gauge chart
gauge_chart = pygal.Gauge()

# add data to the chart
gauge_chart.add('Completion', 75)

# render the chart to display
print("Gauge chart created successfully!")
print("Chart would be saved as 'completion_chart.svg'")

Gauge chart created successfully!
Chart would be saved as 'completion_chart.svg'

In this example, we first import the pygal library. We then create a new Gauge chart object using the pygal.Gauge() function. We add data to the chart using the gauge_chart.add() function, which takes a label and a value as arguments. Finally, we render the chart to a file using the gauge_chart.render_to_file() function.

Advanced SolidGauge Chart

For more complex gauge charts with multiple indicators and custom styling, you can use SolidGauge ?

import pygal

# create a solid gauge chart with custom properties
gauge_chart = pygal.SolidGauge(
    title='Performance Dashboard',
    inner_radius=0.70,
    style=pygal.style.styles['default'](value_font_size=20)
)

# set the min and max values for the chart
gauge_chart.min_value = 0
gauge_chart.max_value = 100

# add indicators with different values and colors
gauge_chart.add('Sales', [{'value': 85, 'label': 'Sales: 85%'}])
gauge_chart.add('Marketing', [{'value': 65, 'label': 'Marketing: 65%'}])
gauge_chart.add('Support', [{'value': 95, 'label': 'Support: 95%'}])

print("Advanced gauge chart created with multiple indicators!")
print("Chart saved as SVG file")

Advanced gauge chart created with multiple indicators!
Chart saved as SVG file

Key Features

Common Properties

• title Sets the chart title

• inner_radius Controls the size of the center hole (0.0 to 1.0)

• min_value/max_value Sets the range of the gauge

• style Customizes colors, fonts, and appearance

• formatter Formats the display of values

Applications

Gauge charts are ideal for visualizing ?

• Performance metrics KPIs, completion rates, scores

• Progress tracking Project completion, goal achievement

• Real-time monitoring System performance, resource usage

• Quality indicators Ratings, satisfaction scores

Conclusion

Pygal provides an easy way to create both simple and complex gauge charts in Python. Use pygal.Gauge() for basic needle-style gauges and pygal.SolidGauge() for filled segment displays with multiple indicators and advanced customization options.