OCaPy

Ocapy is a free scientific, graphing, and engineering calculator for PC implementing the well-known reverse polish notation (RPN) available on Hewlett-Packard calculators. Ocapy stands for an "Original Calculator in Python". The main features are: calculator software running on any windows desktop, laptop, or notebook under RPN (reverse polish notation), optimized use of a totally reconfigurable keyboard, and limited use of the mouse, selectable accuracy using a multiple-precision math library, handling of experimental figures and automatic error propagation calculation, plotter, programmable, HP like SOLVER and HP like MES (Multiple Equations Solver).