This is a fully functioning standard calculator hand-built using QT for Python.
Every aspect of this calculator was designed without using QTDesigner.
This calculator has most of the capabilities of the Standard Windows Calculator. It was meant to serve as a way to experiment with PyQt and get better at writing code in Python.
Some features include basic automatic expression evaluation.
You can also completely edit expressions with the backspace button, even allowing you to change the operator after typing the second operand.