def sum_list(some_list):
    result = 0

    for val in some_list:
        result = result + val

    return result

def list_to_string(some_list):
    result = ""

    for val in some_list:
        result = result + str(val)

    return result

def string_to_list(some_string):
    result = []

    for char in some_string:
        result.append(char)
        
    return result

def multiply_lists(list1, list2):
    result = []

    if len(list1) != len(list2):
        print "Error: lists are not of equal length!"
    else:
        for i in range(len(list1)):
            result.append(list1[i]*list2[i])

    return result