unique_number.py

delivery_id_confirmations = [1,2,3,4,5,6,7,8,9,10,
                             1,2,3,5,6,7,8,9,10]  # 4 missing

def find_unique_id(id_array):
    for num in id_array:
        if id_array.count(num) == 1:
            print "Missing Delivery Man ID: {0}".format(num)


if __name__ == '__main__':
    find_unique_id(delivery_id_confirmations)