Set update() in Python to do union of n arrays

In this tutorial, we will use the set.update() method to find the union of multiple arrays. This method efficiently combines arrays while automatically removing duplicates, returning a one-dimensional array with all unique values.

What is set.update()?

The update() method adds elements from an iterable (like a list or array) to an existing set. It automatically handles duplicates by keeping only unique values.

Syntax

set.update(iterable)

Example

Let's see how to union multiple arrays using set.update() ?

# initializing the arrays
arrays = [[1, 2, 3, 4, 5], [6, 7, 8, 1, 2, 3, 4, 5], [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]]

# empty set
result = set()

# iterating over the arrays
for array in arrays:
    # updating the set with elements from current array
    result.update(array)

# converting set to list and printing
print(list(result))

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

How It Works

The algorithm follows these steps:

• Create an empty set to store unique elements
• Iterate through each array in the input
• Use update() to add elements from current array to the set
• Convert the final set back to a list

Alternative Approach Using Union Operator

You can also use the union operator (|) for the same result ?

arrays = [[1, 2, 3, 4, 5], [6, 7, 8, 1, 2, 3, 4, 5], [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]]

result = set()
for array in arrays:
    result = result | set(array)

print(list(result))

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Comparison

Conclusion

The set.update() method provides an efficient way to union multiple arrays by automatically handling duplicates. It's memory-efficient and performs well for large datasets compared to other approaches.