def is_unique(seq):
    '''Returns True if every item in the seq is unique, False otherwise.'''
    try:
        s = set(seq)
        return len(s) == len(seq)
    except TypeError:
        buf = []
        for item in seq:
            if item in buf:
                return False
            buf.append(item)
        return True
Returns True if every item in the seq is unique, False otherwise.