Reversable Dict. Accessible via key or value.

dict.py

import collections
class Dict(collections.MutableMapping):
    def __init__(s, *args, **kwargs):
        s.fwd = dict(*args, **kwargs)
        s.rev = dict((v, k) for k, v in s.fwd.items())
    def __delitem__(s, k):
        if k in s.fwd: return s.rev.pop(s.fwd.pop(k))
        if k in s.rev: return s.fwd.pop(s.rev.pop(k))
        raise KeyError, "%s not found." % k
    def __getitem__(s, k):
        if k in s.fwd: return s.fwd[k]
        if k in s.rev: return s.rev[k]
        raise KeyError, "%s not found." % k
    def __iter__(s): return iter(s.fwd)
    def __repr__(s): return repr(s.fwd)
    def __len__(s): return len(s.fwd)
    def __setitem__(s, k, v):
        try: s.__delitem__(k)
        except KeyError: pass
        try: s.__delitem__(v)
        except KeyError: pass
        s.fwd[k] = v
        s.rev[v] = k