# Stack Arrays Horizontally – NumPy

Contents

## NumPy – Stack arrays horizontally

To stack two or more arrays horizontally in NumPy, we can use numpy.hstack() function. Pass the arrays in a tuple as argument to hstack() function.

For example, we want to stack arrays a, b, and c horizontally using hstack() function, use the following expression.

``numpy.hstack((a, b, c))``

## Examples

### 1. Stack two arrays horizontally

In the following program, we take two numpy arrays and stack them horizontally.

Python Program

``````import numpy as np

arr1 = np.array([[1, 2], [3, 4]])
arr2 = np.array([[5, 6], [7, 8]])

output = np.hstack((arr1, arr2))

print('array 1\n', arr1)
print('array 2\n', arr2)
print('stacking horizontally...\n', output)``````
Run Code Copy

Output

``````array 1
[[1 2]
[3 4]]
array 2
[[5 6]
[7 8]]
stacking horizontally...
[[1 2 5 6]
[3 4 7 8]]``````

### 2. Stack three arrays horizontally

In the following program, we take two numpy arrays and stack them horizontally.

Python Program

``````import numpy as np

arr1 = np.array([[1, 2], [3, 4]])
arr2 = np.array([[5, 6], [7, 8]])
arr3 = np.array([[9, 10],[11, 12]])

output = np.hstack((arr1, arr2, arr3))

print('array 1\n', arr1)
print('array 2\n', arr2)
print('array 3\n', arr3)
print('stacking horizontally...\n', output)``````
Run Code Copy

Output

``````array 1
[[1 2]
[3 4]]
array 2
[[5 6]
[7 8]]
array 3
[[ 9 10]
[11 12]]
stacking horizontally...
[[ 1  2  5  6  9 10]
[ 3  4  7  8 11 12]]``````

## Summary

In this NumPy Tutorial, you learned how to access elements of a numpy array using indexing operator.

## Related Tutorials

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