[Spivak]

I'm so confused by this, Python is really fast. This isn't to say that other languages aren't a lot faster but I can afford to be so ungodly wasteful with CPU bound tasks (on "leaf" programs don't worry I'm not doing this in libraries to be consumed by others) because it literally doesn't matter. The IO to call print(), write a log, or read a file on disk dwarfs the time actually spent running Python code and this is before using the new JIT.

I wouldn't number crunch in Python without something like numpy because you'll pay the cost of Python's dynamism for nothing but a lot of work has gone into making Python's primitives and standard library performant. I steal algorithms from CPython all the time.