Python: finding keys with unique values in a dictionary?

Question

I receive a dictionary as input, and want to return a list of keys for which the dictionary values are unique in the scope of that dictionary.

I will clarify with an exa

Answer 1

Here is a solution that only requires traversing the dict once:

def unique_values(d):
    seen = {} # dict (value, key)
    result = set() # keys with unique values
    for k,v in d.iteritems():
        if v in seen:
            result.discard(seen[v])
        else:
            seen[v] = k
            result.add(k)
    return list(result)