"On python" can mean a few different things. It can mean a straight port, running in the python interpreter, or it can mean Cython (or similar) with all of the

"On python" can mean a few different things. It can mean a straight port, running in the python interpreter, or it can mean Cython (or similar) with all of the tight loops running as auto-generated compiled C code. Numpy is a great example of this; all of the numerical operations are running on very fast compiled code, and being good at writing fast numpy involves knowing the ins and outs of how to minimize passing information between the slow python interpreter and the fast numerical engines. You want to just do all of the computation 'inside' of numpy, and then get the result at the end.