# How to add a border around a NumPy array?

• Last Updated : 01 Oct, 2020

Sometimes we need to add a border around a NumPy matrix. Numpy provides a function known as ‘numpy.pad()’ to construct the border. The below examples show how to construct a border of ‘0’ around the identity matrix.

Syntax :

```numpy.pad(array, pad_width, mode='constant', **kwargs)
```

Example 1: Construct a border of 0s around 2D identity matrix

## Python3

 `# importing Numpy package``import` `numpy as np`` ` `# Creating a 2X2 Numpy matrix``array ``=` `np.ones((``2``, ``2``))`` ` `print``(``"Original array"``)``print``(array)`` ` `print``(``"\n0 on the border and 1 inside the array"``)`` ` `# constructing border of 0 around 2D identity matrix``# using np.pad()``array ``=` `np.pad(array, pad_width``=``1``, mode``=``'constant'``,``               ``constant_values``=``0``)`` ` `print``(array)`

Output: In the above examples, we construct a border of 0s around the 2-D NumPy matrix.

Example 2: Construct a border of 0s around 3D identity matrix

## Python3

 `# importing Numpy package``import` `numpy as np`` ` `# Creating a 3X3 Numpy matrix``array ``=` `np.ones((``3``, ``3``))`` ` `print``(``"Original array"``)``print``(array)`` ` `print``(``"\n0 on the border and 1 inside the array"``)`` ` `# constructing border of 0 around 3D identity matrix``# using np.pad()``array ``=` `np.pad(array, pad_width``=``1``, mode``=``'constant'``,``               ``constant_values``=``0``)`` ` `print``(array)`

Output: In the above examples, we construct a border of 0s around the 3-D NumPy matrix.

Example 3: Construct a border of 0s around 4D identity matrix

## Python3

 `# importing Numpy package``import` `numpy as np`` ` `# Creating a 4X4 Numpy matrix``array ``=` `np.ones((``4``, ``4``))`` ` `print``(``"Original array"``)``print``(array)`` ` `print``(``"\n0 on the border and 1 inside the array"``)`` ` `# constructing border of 0 around 4D identity matrix``# using np.pad()``array ``=` `np.pad(array, pad_width``=``1``, mode``=``'constant'``,``               ``constant_values``=``0``)`` ` `print``(array)`

Output: In the above examples, we construct a border of 0s around the 4-D NumPy matrix.

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