Simple, safe single expression evaluator library (Python 3)

 Quick single file library for easily adding evaluatable expressions into
 Python projects.
 .
 Short, easy to use, safe and reasonably extensible expression evaluator.
 Designed for things like in a website where you want to allow the user to
 generate a string, or a number from some other input, without allowing full
 eval() or other unsafe or needlessly complex linguistics.
 .
 This package is targeting Python version 3.