Design System in Python

At its core, fast-gov-uk is an implementation of the GOV.UK Design System in Python.

We do this using the excellent FastHTML library, which provides a simple way to create interactive HTML components using pure Python.

Here is an example of a FastHTML component -

def H1(text, size="l", caption="", **kwargs) -> fh.FT:
   return fh.H1(
      text,
      fh.Span(caption, cls=f"govuk-caption-{size}") if caption else "",
      cls=f"govuk-heading-{size}",
      **kwargs,
   )

Like H1 above, we have implemented all the components from the GOV.UK Design System in pure Python.

In addition, we have created some higher-level components like Page - that help you build complete GDS-style pages quickly and easily.

Finally, we have also created some components that are not part of the GOV.UK Design System, but are commonly used in GOV.UK services e.g. EmailInput and other components in the contrib module.

These components are organised into modules according to their type -

• Pages
• Typography
• Components
• Navigation
• Inputs
• Contrib
• Utils