Between mybinder and JupyterHub, you have plenty of online resources at your disposal for running very nice Python environments and testing out small snippets of code. But you don't want "nice." You want the real deal. It's certainly more than possible to ace this course without ever installing Python on your local machine, but just in case you really want to give it a shot...
It's pretty easy, actually. Well, if you wanted to install base Python, that can be a royal headache; different operating systems (Windows vs Unix), different versions (Python 2 vs Python 3), and how to get that pesky $PATH variable to cooperate? Fortunately, my recommendation is not to use base Python.
Instead, we'll use a Python distribution: Anaconda. Anaconda is basically a fully-functional, prepackaged Python distribution that is ready-built for any of the three major operating systems: Windows, OS X, and Linux. It comes with a ton of very useful third-party packages, so (at least in this class) we won't even need to worry about installing anything beyond Anaconda itself. But it also comes with a couple package managers, so even if you wanted or needed extra packages, the tools are already provided. Pretty sweet deal!
Go to the Anaconda downloads page: https://www.continuum.io/downloads . Click on the link for your operating system, and download the graphical installer (you'll most likely want 64-bit).
MAKE SURE YOU DOWNLOAD ANACONDA FOR PYTHON 3.
Once the install is finished, let's test that it worked: Fire up a command prompt / Terminal window. Type python.
If all is well, you should see exactly what we saw in the JupyterHub terminal.