.repeat()

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Published Apr 8, 2025
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The .repeat() function in NumPy is used to duplicate items in an array. It provides the option to specify the number of times each element appears, and whether that repetition happens across a specific axis or not. If no axis is mentioned, the array is flattened before repeating.

Syntax

numpy.repeat(a, repeats, axis=None)

Parameters:

  • a: The array to work with. This is where the elements come from.
  • repeats: An int or array of ints. If an int, each element of a is repeated that many times. If an array, it must match the length of a (if axis=None) or the length of a along the specified axis.
  • axis (Optional): Sets the direction for repeating.

Return value:

Returns a NumPy array with repeated elements. The shape of the result depends on the shape of a, the repeats value, and whether an axis is specified.

Example 1: Repeating Elements Without Specifying the axis Parameter

Here’s a simple example where each value in a one-dimensional array gets repeated twice:

import numpy as np


# Create an array
arr = np.array([1, 2, 3])


# Repeat each element in the array 2 times
print(np.repeat(arr, 2))

The above code produces the following output:

[1 1 2 2 3 3]

Example 2: Directional Repetition Using the axis Parameter

For multi-dimensional arrays, using the axis parameter controls which direction the repetition flows:

import numpy as np


arr2d = np.array([[1, 2], [3, 4]])


# Repeat each element in the array 2 times along axis 0
print(np.repeat(arr2d, 2, axis=0))


# Repeat each element in the array 2 times along axis 1
print(np.repeat(arr2d, 2, axis=1))

The above code produces the following output:

[[1 2]
 [1 2]
 [3 4]
 [3 4]]
[[1 1 2 2]
 [3 3 4 4]]

Codebyte Example: Repeating Each Element Three Times

This codebyte example repeats every item in an array three times in a row:

Code
Output
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