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Two way python dictionary

Here there is a simple class implementation of Two way Dictionary that uses from native dictionary class of Python. The main idea of that kind of data structure to reach, but side of the data by using other side as the key. It is like bi-directional relation between items.

A dumb use case:

d = TwoWayDict()
d['erogol'] = 13
print d['erogol']
# outputs 13
print d[13]
# outputs erogol

Here is the class implementation. However, keep in mid that this class uses more x2 memory to keep the data with that functionality.

class TwoWayDict(dict):
    def __len__(self):
        return dict.__len__(self) / 2

    def __setitem__(self, key, value):
        dict.__setitem__(self, key, value)
        dict.__setitem__(self, value, key)

Hope this helps in some hinge ­čÖé