We will start extending the unit conversion application by taking a copy of the unitconverter directory and the setup.py scripts from the code written in Chapter 9, Creating Command-line Interfaces (a copy of this code is included in the code downloads for Chapter 9, Creating Command-line Interfaces).

We will then create a new module named gui within the unitconverter module. This will contain the Qt window that will provide a graphical interface to the unit conversion tool and the code that will launch it.

As we have done before, this is done by creating a directory named gui inside the unitconverter directory and a file named __init__.py inside the gui directory.

At this point, the code structure will be identical to that shown in the following image:

We must also install the libraries and tools required to develop the application. This includes the setuptools utility for packaging Python code and the Qt framework and supporting utilities, including Qt Designer, which...