NumPy: Find the union of two arrays

Last update on August 29 2025 12:46:24 (UTC/GMT +8 hours)

Union of Two Arrays

Write a NumPy program to find the union of two arrays. Union will return a unique, sorted array of values in each of the two input arrays.

Pictorial Presentation:

Python NumPy: Find the union of two arrays

Sample Solution:

Python Code:

# Importing the NumPy library with an alias 'np'
import numpy as np

# Creating a NumPy array 'array1'
array1 = np.array([0, 10, 20, 40, 60, 80])

# Printing the contents of 'array1'
print("Array1: ", array1)

# Creating a Python list 'array2'
array2 = [10, 30, 40, 50, 70]

# Printing the contents of 'array2'
print("Array2: ", array2)

# Finding and printing the unique values that are in only one (not both) of the input arrays
print("Unique values that are in only one (not both) of the input arrays:")
print(np.union1d(array1, array2))

Sample Output:

Array1:  [ 0 10 20 40 60 80]                                           
Array2:  [10, 30, 40, 50, 70]                                          
Unique sorted array of values that are in either of the two input array
s:                                                                     
[ 0 10 20 30 40 50 60 70 80]

Explanation:

In the above code –

array1 = np.array([0, 10, 20, 40, 60, 80]): Creates a NumPy array with elements 0, 10, 20, 40, 60, and 80.

array2 = [10, 30, 40, 50, 70]: Creates a Python list with elements 10, 30, 40, 50, and 70.

print(np.union1d(array1, array2)): The np.union1d function returns the sorted union of the two input arrays, which consists of all unique elements from both ‘array1’ and ‘array2’. In this case, the union is [0, 10, 20, 30, 40, 50, 60, 70, 80], so the output will be [ 0 10 20 30 40 50 60 70 80].

For more Practice: Solve these Related Problems:

Compute the union of two arrays using np.union1d and check that the result is unique and sorted.
Create a function that merges two arrays and removes duplicates without using np.union1d.
Compare the union operation on arrays with overlapping and non-overlapping values.
Validate that the union of two arrays contains every distinct element from both inputs.

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