BBP Lesson 11: Interactive Data Visualization with Pygal

:dart: Learning Objectives

By the end of this lesson, you will be able to:

• Understand what data visualization is and why it's important
• Import and use the Pygal module in EduBlocks
• Create three different types of interactive charts: Bar, Pie, and Radar
• Add data to charts using lists
• Customize your charts with titles and labels
• Connect visual blocks to real Python code concepts

Definition: Pygal is a module that can draw interactive charts in Python. It helps us transform numbers and data into beautiful, interactive visualizations! :bar_chart:

Let's Get Started! :rocket:

Understanding Pygal

Think of data visualization like turning boring numbers into colorful stories! :art: Instead of looking at a list of numbers, we can create charts that make patterns and information jump out at us.

Pygal allows us to visualize our data in a human-readable way through various types of charts.

Chart Types We'll Learn Today

Here are the three main charts we'll master in this lesson:

1. Bar Chart - Perfect for comparing different amounts

   • Example: Comparing scores of different players in a game

   

2. Pie Chart - Great for showing parts of a whole

   • Example: Showing how you spend your time during the day

   

3. Radar Chart - Excellent for comparing multiple characteristics

   • Example: Comparing different skills of a video game character

   

:information_source: Remember! Each chart type has its own special purpose. Choose the one that best tells your data's story!

For a list of other supported charts, you can visit the official documentation.

Getting Started with Pygal

Let's learn how to create our first chart! Follow these 5 simple steps:

Step-by-Step Instructions

Step One: Import the Pygal module

• Just like any other modules, we need to import it first
• Drag the import block from the Modules category

:bulb: Python Connection!

In text-based Python, this block creates: import pygal

Step 2: Create your chart variable

• Go to the Graphs category
• Drag the chart declaration block
• Give your chart a meaningful name (like "my_chart" or "game_scores")
• Select the type of chart you want (default is Line chart)

:bulb: Troubleshooting

Make sure your chart name doesn't have spaces! Use underscores instead: my_awesome_chart not my awesome chart

Step 3: Add a title to your chart

• Drag the title block and connect it to your chart
• Type in a descriptive title

Step 4: Add your data

• Drag the .add() block
• The "Label" is the name for your data (like "Player 1" or "Monday")
• The values must be in a list format using square brackets [10, 20, 30]

:information_source: Remember! Even if you have just one value, it must be in a list: [42] not just 42

Step 5: Display your chart

• Use the .render() block to show your chart on the screen

:bulb: Python Connection!

The complete Python code would look like:

python

import pygal
my_chart = pygal.Bar()
my_chart.title = "My First Chart"
my_chart.add("Data Label", [10, 20, 30])
my_chart.render()

Now that we know the steps, let's create some amazing charts!

Bar Charts

• When adding a data entry, a label is represented in a rectangle bar.

• The list for the data entry determines how many bars to present for that label.

Input	Output

Pie Charts

• When adding a data entry, a label is represented in a slice of a pie.

• The list for the data entry determines how many pie fractions to present for that label.

• The total of all the data entries doesn't have to be 10 as shown below. You can have different values and it will display the proportions accordingly.

Input	Output

Radar Charts

• When adding a data entry, a label is plotted as a dot called radii (single data point).

• For Radar Chart, you have to set the x_label for each individual radii.

The list for the data entry determines each plotted x_label dot with a line drawn through them that forms a polygon shape. The x_label must also be a list in a square bracket [], just like the .add() list.

Depending on the type of chart used, some can also have x_label to label the x-axis such as the bar chart and radar chart.

Input

Output

Experimenting with Chart Types

• Try switching the chart type and see how the data is being presented differently.