Python Unique / Distinct Elements Iterator

distinct.py

def distinct(iterable, keyfunc=None):
    seen = set()
    for item in iterable:
        key = item if keyfunc is None else keyfunc(item)
        if key not in seen:
            seen.add(key)
            yield item

if __name__ == '__main__':
    x = [0, 0, 1, 0, 1, 2, 2, 1, 0]
    assert list(distinct(x)) == [0, 1, 2]
    x = ['', 'a', 'abc', 'cat', 'dog', 'hi']
    assert list(distinct(x, len)) == ['', 'a', 'abc', 'hi']