def last_element(some_list):
    '''Return the last element of some_list'''
    if len(some_list) == 0:
        return None
    else:
        return some_list[-1]


def delete_first(some_list):
    '''Delete the first element of some_list'''
    del some_list[0]


def list_add(some_list, el):
    '''Add el to the end of some_list'''
    some_list.append(el)

    # The below does NOT do the same thing!
    #
    # some_list = some_list + el
    #
    # This makes a *copy* of the list and adds to the copy.
    # The original list (that was passed as the argument) is unchanged.