import numpy as np

def mean(x):
    N = np.size(x) # x.size
    s = 0.0
    for i in range(N):
        s += x[i]
    return s / N

rng = np.random.default_rng() # instantiating an RNG class
x = rng.normal(size = 10) # use rng instance to generate random numbers => ndarray
x

array([ 0.53768287,  0.48044289,  0.41968892,  0.53617612,  0.12008546,
        2.36768986,  0.17752883,  0.68915822,  0.07121943, -0.29874026])

np.isclose(mean(x), np.mean(x)) # don't == floats/doubles

True