numpy.vstack() in python (original) (raw)

Last Updated : 12 Jun, 2025

numpy.vstack() is a function in NumPy used to stack arrays vertically (row-wise). It takes a sequence of arrays as input and returns a single array by stacking them along the vertical axis (axis 0).

**Example: Vertical Stacking of 1D Arrays Using numpy.vstack()

Python `

import numpy as geek

a = geek.array([ 1, 2, 3] ) print ("1st Input array : \n", a)

b = geek.array([ 4, 5, 6] ) print ("2nd Input array : \n", b)

res = geek.vstack((a, b)) print ("Output vertically stacked array:\n ", res)

`

Output

1st Input array : [1 2 3] 2nd Input array : [4 5 6] Output vertically stacked array: [[1 2 3] [4 5 6]]

The two 1D arrays a and b are stacked vertically using **np.vstack(), combining them into a 2D array where each input array forms a row.

Syntax

numpy.vstack(tup)

**Parameters:

• **tup: [sequence of ndarrays] Tuple containing arrays to be stacked. The arrays must have the same shape along all but the first axis.

**Return: [stacked ndarray] The stacked array of the input arrays.

Vertical Stacking of 2D Arrays Using numpy.vstack()

This code shows how to vertically stack two 2D arrays using numpy.vstack() resulting in a combined 2D array.

Python `

import numpy as geek

a = geek.array([[ 1, 2, 3], [ -1, -2, -3]] ) print ("1st Input array : \n", a)

b = geek.array([[ 4, 5, 6], [ -4, -5, -6]] ) print ("2nd Input array : \n", b)

res = geek.vstack((a, b)) print ("Output stacked array :\n ", res)

`

Output

1st Input array : [[ 1 2 3] [-1 -2 -3]] 2nd Input array : [[ 4 5 6] [-4 -5 -6]] Output stacked array : [[ 1 2 3] [-1 -2 -3] [ 4 5 6] [-4 -5 -6]]

Two 2D arrays a and b are vertically stacked, creating a new 2D array where each original array becomes a set of rows in the resulting array.