[hharrison]

In MATLAB, R, or numpy, it's the difference between `mean(n)` and manually looping. It's not an issue of algorithmic efficiency, it's an issue of lost productivity because they don't even write a function to reuse (all they understand is scripting) they recode the loop every single time they have to sum or take the mean of something.

[gaius]

Well it is because NumPy and friends do all the heavy-lifting in hand-tuned C. dis() your Python function for taking a mean and see the difference, it's huge.