1. Calculating mean ：

import numpy as np
from time import time
a = list(range(1, 100000))
mean1 = np.mean(a) # method 1
mean2 = sum(a) / len(a) # method 2

In terms of time consuming ,np.mean() Time will be longer than the second method . therefore , It is not recommended to use the mean value np modular .

2. Variance estimation ：

When you look at the formula of variance, you know that you can't write without adding for loop , So here we recommend np modular

import numpy as np
from time import time
a = list(range(1, 100000))
s2 = np.var(a)

Direct use np.var() We can find the variance .

3. Find the difference of mark ：

This is just a short square , You can also use np.std().