If you haven’t encountered RPN before, it is an easy way to express math without ambiguity ... If the token is an operator, check to see if it is lower in precedence than the top of the operator ...

That was [gnebehay’s] thought when his university studies were too high level, so he decided to write an arithmetic expression parser in Python ... Tricky. Precedence is the other problem.

Python supports unary operators for no change and negation, + and -, respectively; and binary arithmetic operators +, -, *, /, //, %, and **, for addition ...