One vs Two Dimensional Array

import numpy as np

a = np.array([1, 2, 3, 4])

a

array([1, 2, 3, 4])

a.shape

(4,)

b = np.array([
    [1], [2], [3], [4]
])

b

array([[1],
       [2],
       [3],
       [4]])

b.shape

(4, 1)

Diff between (4, ) and (4, 1)

The difference between (4,) and (4,1) is that the first is the shape of a one-dimensional array, while the second is the shape of a 2-dimensional array whose 2nd dimension has length 1.