# Lists

def is_seq(value):

    return (isinstance(value, list) or isinstance(value, tuple)

        or isinstance(value, set))

def clear(list_):

    while True:

        try: list_.pop()

        except IndexError: break

def uniqify(list_):

    '''Removes duplicates from an iterable. Preserves order.'''

    existing = set()

    new_list = []

    for value in list_:

        if value not in existing:

            existing.add(value)

            new_list.append(value)

    return new_list