How to get the number of dimensions of a matrix using NumPy in Python?

In this article, we will discuss how to get the number of dimensions of a matrix using NumPy. It can be found using the ndim parameter of the ndarray() method.

Syntax: no_of_dimensions = numpy.ndarray.ndim

Approach:

• Create an n-dimensional matrix using the NumPy package.
• Use ndim attribute available with the NumPy array as numpy_array_name.ndim to get the number of dimensions.
• Alternatively, we can use the shape attribute to get the size of each dimension and then use len() function for the number of dimensions.
• Use numpy.array() function to convert a list to a NumPy array and use one of the above two ways to get the number of dimensions.

Get the Number of 1-Dimensions of a Matrix

Creating a 1D array using np.arrange and printing the dimension of an array.

Python3

import numpy as np

# create numpy arrays
# 1-d numpy array
_1darr = np.arange(4)
print(_1darr)

# printing the 1-dimensions numpy array
print("Dimensions in _1darr are: ", _1darr.ndim)

Output:

[0 1 2 3]
Dimensions in _1darr are:  1v

Get the Number of 2-Dimensions of a Matrix

Creating a 2D array using np.arrange and printing the dimension of an array.

Python3

import numpy as np

x = np.arange(12).reshape((3, 4))
print("Matrix: \n", x)

print("Dim: ", x.ndim)

Output:

Matrix: 
 [[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]]
Dim:  2

Get the Number of 3-Dimensions of a Matrix

Creating a 3D array using np.arrange and np.reshape. After that, we are printing the dimension of an array using shape and len().

Python3

import numpy as np

# 3-d numpy array
_3darr = np.arange(18).reshape((3, 2, 3))

# printing the dimensions of each numpy array
print("Dimensions in _3darr are: ", _3darr.ndim)
print(_3darr)

# numpy_arr.shape is the number of elements in
# each dimension numpy_arr.shape returns a tuple
# len() of the returned tuple is also gives number
# of dimensions
print("Dimensions in _3darr are: ", len(_3darr.shape))

Output:

Dimensions in _3darr are:  3
[[[ 0  1  2]
  [ 3  4  5]]

 [[ 6  7  8]
  [ 9 10 11]]

 [[12 13 14]
  [15 16 17]]]
Dimensions in _3darr are:  3

Convert a list to a Numpy Array and Get a Dimensions of a Matrix

Creating a list of 1D and 2D, using np.arrange we are converting it into a np.array and printing the dimension of an array.

Python3

import numpy as np

# Use numpy.array() function to convert a list to
# numpy array
__1darr = np.array([5, 4, 1, 3, 2])
__2darr = np.array([[5, 4],[1,2], [4,5]])
print("Dimensions in __1darr are: ", __1darr.ndim)
print("Dimensions in __2darr are: ", __2darr.ndim)

Output:

Dimensions in __1darr are:  1
Dimensions in __2darr are:  2