Separate Evens and Odds into Two Lists in Python

Split a list of numbers into two lists containing even and odd numbers using a simple loop and the modulo operator.

Easy Python 3.9+ Aug 9, 2026 Lists & loops 13 views 0 copies

lists loops modulo partitioning split

Python code

15 lines

Python 3.9+

def separate_evens_odds(numbers):
    evens = []
    odds = []
    for num in numbers:
        if num % 2 == 0:
            evens.append(num)
        else:
            odds.append(num)
    return evens, odds

if __name__ == "__main__":
    nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
    evens, odds = separate_evens_odds(nums)
    print(f"Evens: {evens}")
    print(f"Odds: {odds}")

Output

stdout

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

How it works

The function iterates over each number in the input list. The % (modulo) operator returns the remainder after division; if num % 2 is 0, the number divides evenly by 2 and is even, so it's appended to evens, otherwise it goes to odds. Appending to lists is O(1) on average, making this approach linear in time complexity O(n). Returning a tuple (evens, odds) lets you unpack the two lists directly in the caller.

Common mistakes

Using `if num % 2:` to check for even (that catches odd numbers instead)
Forgetting that 0 is even and should go to the evens list
Mutating the input list instead of creating new lists

Variations

Use list comprehensions: `evens = [n for n in numbers if n % 2 == 0]` and `odds = [n for n in numbers if n % 2 != 0]`
Use `filter` with lambda for a functional approach

Real-world use cases

Segmenting transaction amounts into even/odd buckets for fraud detection analysis.
Partitioning sensor readings like channel IDs for load-balanced processing.
Grouping test case indices into separate queues for parallel execution.

Separate Evens and Odds into Two Lists in Python

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

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Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

More from Lists & loops

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