Examples of how to get the number of elements in an array (or matrix) with numpy in python

### Create a matrix

Let's create a simple matrix to illustrate how to get the number of elements

`import numpy as np`

`A = np.random.randint(5, size=(4, 6))`

`print(A)`

returns

`[[3 0 0 4 3 3]`

`[4 2 3 4 2 2]`

`[0 1 1 4 1 0]`

`[4 3 0 0 3 3]]`

### Get the number of elements using size

To get the number of elements in the matrix A, a solution is to use the method size:

`print(A.size)`

`24`

### Get the number of elements using shape

`print(A.shape[0]*A.shape[1])`

`24`

### Get the number of unique elements

To go further we can also get unique elements inside the matrix A:

`print(np.unique(A))`

returns

`[0 1 2 3 4]`

and then print the number for each unique element:

`for e in np.unique(A):`

`print('Number of {}: '.format(e), A[A==e].size)`

returns

`Number of 0: 6`

`Number of 1: 3`

`Number of 2: 3`

`Number of 3: 7`

`Number of 4: 5`