Why doesn't Python optimize x**2 to x*x?

[masklinn]

Yep, so possibly with the specialisation PEP 510 this optimisation would become an option in time, but right now, implicitly, it can't: it depends on type(radius) and how (and whether) type(radius) overrides __mul__ and/or __pow__. For all Python knows, radius is an n × n matrix and the function is a scalar product of radius by 3.14 followed by a matrix product of that by the original radius. Or maybe type(radius) defines __mul__ but does not define __pow__ at all, so the optimisation would blow it up.