On Windows, you're right. And when you're inside a virtual environment on a Mac, you're also right--there is no need to type python3 once you're inside a virtual environment. However, if you're outside a virtual environment on a Mac, just typing python will refer to python 2.7 not python 3.x.x. I stuck with python3 for consistency's sake and to be super explicit, in case you're a Mac user.