Concatenate (or clone) a NumPy array N times

Learn, how to Concatenate (or clone) a NumPy array N times? By Pranit Sharma Last updated : October 10, 2023

NumPy is an abbreviated form of Numerical Python. It is used for different types of scientific operations in python. Numpy is a vast library in python which is used for almost every kind of scientific or mathematical operation. It is itself an array which is a collection of various methods and functions for processing the arrays.

Problem statement

Suppose we need to work on a MxN NumPy matrix by cloning an Mx1 ndarray N times, we need to find an appropriate approach for this.

NumPy - Concatenate (or clone) an array N times

For this purpose, we first need to define a value of N, and then we will create a NumPy array. Now we will use numpy.vstack() method. This method stacks arrays in sequence vertically (row wise).

This is equivalent to concatenation along the first axis after 1-D arrays of shape (N,) have been reshaped to (1, N). This function makes the most sense for arrays with up to 3 dimensions. For instance, for pixel-data with a height (first axis), width (second axis), and r/g/b channels (third axis). The functions concatenate, stack and block provide more general stacking and concatenation operations.

Let us understand with the help of an example,

Python program to concatenate (or clone) a NumPy array N times

# Import numpy
import numpy as np

# Creating a numpy array
arr = np.array([1,2,3,4,5])

# Display original array
print("Orignal array:\n",arr,"\n")

# Defining a value of N
N = 5

# Using vstack method
res = np.vstack([arr]*N)

# Display result


The output of the above program is:

Example: Concatenate (or clone) a NumPy array N times

Python NumPy Programs »

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