Comment by dragonwriter

> Numpy has mean and variance functions built in for arrays.

Even outside of Numpy, the stdlib has the statistics packages which provides mean, variance, population/sample standard deviation, and other statistics functions for normal iterables. The attempt to make Python out-of-the-box code look bad was either deliberately constructed to exaggerate the problems complained of, or was the product of a very convenient ignorance of the applicable parts of Python and its stdlib.