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#!/usr/bin/env python3
class bidict(dict):
def __init__(self, *args, **kwargs):
super(bidict, self).__init__(*args, **kwargs)
self.inverse = {}
for key, value in self.items():
self.inverse.setdefault(value, []).append(key)
def __setitem__(self, key, value):
if key in self:
self.inverse[self[key]].remove(key)
super(bidict, self).__setitem__(key, value)
self.inverse.setdefault(value, []).append(key)
def __delitem__(self, key):
self.inverse.setdefault(self[key], []).remove(key)
if self[key] in self.inverse and not self.inverse[self[key]]:
del self.inverse[self[key]]
super(bidict, self).__delitem__(key)
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