It actually isn't saying that. What do you think Python is made of, under the hood? It's C modules. The argument is not that NumPy is written in C, but that it

It actually isn't saying that. What do you think Python is made of, under the hood? It's C modules. The argument is not that NumPy is written in C, but that it amortizes the cost of Python overhead over multiple data, rather than incur it on each datum.