What is the numpy.eye() function in Python?

Overview

The numpy.eye() function in Python is used to return a two-dimensional array with ones (1) on the diagonal and zeros (0) elsewhere.

Syntax

numpy.eye(N, M=None, k=0, dtype=<class 'float'>, order='C', *, like=None)

Parameters

The numpy.eye() function takes the following parameter values:

  • N: This represents the number of rows we want in the output array.
  • M: This represents the number of columns we want in the output array. This is optional.
  • k: This represents the index of the diagonal. 0 is the default value and the main diagonal. This is optional.
  • dtype: This represents the data type of array to be returned. This is optional.
  • order: This represents whether the output should be stored in C or F order in memory. This is optional.
  • like: This is the array prototype or array_like object.

Return value

The numpy.eye() function returns a type of array where all the elements are equal to 0, except for the kthk^{th} diagonal, whose values are equal to 1.

Example 1

import numpy as np
# An array with 3 rows with with the ones starting at the index i.e fron the second column
myarray = np.eye(3, k=1)
print(myarray)

Explanation

  • Line 1: We import the numpy module.
  • Line 4: We use the numpy.eye() function to create an array with 3 rows and the ones should start on index 1 of the array. The output is stored in a variable myarray.
  • Line 6: We print the variable myarray.

Example 2

import numpy as np
# An array with 2 rows and integer data type
myarray = np.eye(2, dtype=int)
print(myarray)

Explanation

  • Line 1: We import the numpy module.
  • Line 4: We use the numpy.eye() function to create an array with 2 rows. The data type of the array should be integer. The output is stored in a variable myarray.
  • Line 6: We print the variable myarray.