odd_occurences.py

from collections import Counter

def odd_occurences(elements):
    """returns the value of the unpaired element in odd number of elements.
    
    :param elements: a list of integers.
    :rtype: int
    """
    odd_values = [value for value, count in Counter(A).iteritems() if count % 2 != 0]
    # The task description assumes there should be one and only one odd value in the given list
    # solution returns zero for an empty list
    return odd_values[0] if odd_values else 0