rsdict.py

class RandomSampleDict(object):

    def __init__(self):
        self.data     = {}
        self.cache_ik = {}
        self.cache_ki = {}
        self.track    = []

    def lookup(self, key):
        return self.data[key]


    def set(self, key, value):
        self.data[key] = value


    def add(self, key, value):
        self.data[key] = value
        if len(self.track) == 0:
            i = len(self.data) - 1
        else:
            i = self.track.pop()
            
        self.cache_ik[i] = key
        self.cache_ki[key] = i


    def delete(self, number):
        del self.data[key]
        i = self.cache_ik[i]
        del self.data_ik[i]
        del self.data_ki[key]

        self.track.append(i)


    def random_sample_key(self):
        key = None
        while key is None:
            i = randint(0, len(self.data))
            if i in self.cache_ik:
                return self.cache_ik[i]