CSS Framework

Using Bootstrap

Many CSS frameworks make styling applications a little easier, especially if we find graphic design challenging. We’ll take a quick look at Bootstrap, a popular CSS framework with several predefined CSS classes, which can help maintain the consistency of the visual aspects of our application. Bootstrap has a lot of features, so for now we’ll focus on the CSS classes it has and give us an idea on how to incorporate them into our Python web application.

Adding Bootstrap to the project

Bootstrap generally relies on a grid system for layout and uses classes to represent style attributes. To apply any mix of styles to a given element, we will add each style class that represents the attributes we want to apply. First, we need to add the Bootstrap stylesheet from the online hosted location to our index.html file in the widget below.

Adding CSS to our application

We can then apply the Bootstrap classes to our Python file.

This time, our application takes on a whole new look since we are using the style theming of the Bootstrap framework, as we see in the widget.

We’ll notice that we no longer have any CSS style properties in our code. All styling is now applied using Bootstrap class names to the elements. In some ways, the classes are just shorter and easier to read versions of the style attributes we were using before. We stack the classes as needed to achieve the desired effect.

Looking at our Edit button as an example, we can break down what each class is doing:

'className': 'btn btn-primary btn-sm mr-2'

• btn: Formats the element as a button.
• btn-primary: Uses the Bootstrap primary color for the button (blue).
• btn-sm: Uses the smaller version of a button.
• mr-2: Adds in a level 2 margin on the right side of the button.

In Bootstrap, some classes apply to specific types of elements, like the ones that start with btn- for button elements. Some classes are universal, like the ones for spacing, as in mr for right margins. The Bootstrap framework has a relatively short learning curve, and we can get highly styled pages without having to fight as many common CSS issues.`

We changed the code by using the HTML form element as our top-level container, then we added an HTML div element, and assigned the Bootstrap container class. This allows us to utilize the Bootstrap grid system to control the layout and move the item list out of the form itself.

We modified our list from an ordered list ol to an unordered list ul. This just removed the numbers on the list items to work better with the Bootstrap layout.