In this tutorial, we will look at how to check if a numpy matrix (a 2d numpy array) is a square matrix or not with the help of some examples.

### What is a square matrix?

A matrix is said to be a square matrix if the number of rows is equal to the number of columns in the matrix. The following image shows a square matrix and a non-square matrix.

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You can see that the number of rows and columns in a square matrix is the same, hence the name square.

## How to check if a matrix is a square matrix in Numpy?

To check if a matrix is a square matrix or not, use the `numpy.ndarray.shape`

property. For a 2d array, the `.shape`

property returns a `(m, n)`

tuple where `m`

is the number of rows and `n`

is the number of columns. To check if the matrix is square or not, simply check if `m`

is equal to `n`

or not.

The following is the syntax –

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import numpy as np # check if the matrix ar is square len(ar.shape) == 2 and ar.shape[0] == ar.shape[1]

In the above syntax, we’re basically checking if the array is a 2d array with the same number of rows and columns.

Let’s now look at some examples of using the above syntax –

### Example

Let’s create a square matrix and check if the above method identifies it correctly or not.

import numpy as np # create a square matrix ar = np.array([ [1, 2], [3, 4] ]) # check if the matrix ar is square print(len(ar.shape) == 2 and ar.shape[0] == ar.shape[1])

Output:

True

Here, we created a 2×2 square matrix and used the above method. We get `True`

as the output indicating the array `ar`

is a square matrix.

Let’s look at an example where the matrix is not a square matrix.

import numpy as np # create a matrix ar = np.array([ [1, 2, 3], [4, 5, 6] ]) # check if the matrix ar is square print(len(ar.shape) == 2 and ar.shape[0] == ar.shape[1])

Output:

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False

Here, we applied the method on a 2×3 matrix. We get `False`

as the output which indicates that the matrix `ar`

is not a square matrix.

Note that if you apply this method on a non-2d array, you’ll get `False`

as the result.

import numpy as np # create a matrix ar = np.array([1, 2, 3, 4]) # check if the matrix ar is square print(len(ar.shape) == 2 and ar.shape[0] == ar.shape[1])

Output:

False

You might also be interested in –

- How to check if a matrix is a diagonal matrix in Numpy?
- Numpy – Check if Matrix is a Lower Triangular Matrix
- Numpy – Check if Matrix is an Upper Triangular Matrix

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