class TwoWay:

    def __init__(self):
        self.d = {}

def add(self, k, v):
    self.d[k] = v
self.d[v] = k

def remove(self, k):
    self.d.pop(self.d.pop(k))

def get(self, k):
    return self.d[k]
A data-structure for 1:1 mappings in python?