# How to get the number of dimensions of a matrix using numpy in python ?

Published: October 17, 2019

Exemple de comment déterminer le nombre de dimensions d'une matrice en python:

### Get the number of dimensions of a matrix

Let's consider the following matrix:

````>>> import numpy as np`
`>>> A = np.array([[3,9,4],[5,8,1],[9,2,5]])`
`>>> A`
`array([[3, 9, 4],`
`       [5, 8, 1],`
`       [9, 2, 5]])`
```

To get the shape of the matrix, a solution is to first use shape:

````>>> A.shape`
`(3, 3)`
```

and then get the number of dimensions of the matrix using len:

````>>> len(A.shape)`
`2`
```

### Example

Let's consider a matrix of dimension 1 or 2

Transpose the matrix if the dimension of the matrix = 2 and the number of columns > number of lines:

````>>> def data_preparation(input_x):`
`...     input_x_shape = input_x.shape`
`...     if len(input_x_shape) == 2:`
`...             if input_x_shape[1] > input_x_shape[0]: `
`...                     input_x = input_x.T`
`...     return input_x`
`... `
`>>> input_x = np.arange(9)`
`>>> input_x`
`array([0, 1, 2, 3, 4, 5, 6, 7, 8])`
`>>> data_preparation(input_x)`
`array([0, 1, 2, 3, 4, 5, 6, 7, 8])`
`>>> input_x = np.arange(20)`
`>>> input_x = input_x.reshape(2,10)`
`>>> data_preparation(input_x)`
`array([[ 0, 10],`
`       [ 1, 11],`
`       [ 2, 12],`
`       [ 3, 13],`
`       [ 4, 14],`
`       [ 5, 15],`
`       [ 6, 16],`
`       [ 7, 17],`
`       [ 8, 18],`
`       [ 9, 19]])`
`>>>`
```