Any interest in an itertools de-duping function? I find I have to write 
this over and over for different projects:

def deduped(iter,key=None):
    keys = set()
    for x in iter:
        if key:
            k = key(x)
        else:
            k = x
        if k in keys:
            continue
        keys.add(k)
        yield(x)