Exposing `defaultdict` as a regular `dict`

Question

I am using defaultdict(set) to populate an internal mapping in a very large data structure. After it\'s populated, the whole structure (including the mapping) i

Answer 1

You could make a class that holds a reference to your dict and prevent setitem()

from collections import Mapping

class MyDict(Mapping):
    def __init__(self, d):
        self.d = d;

    def __getitem__(self, k):
        return self.d[k]

    def __iter__(self):
        return self.__iter__()

    def __setitem__(self, k, v):
        if k not in self.d.keys():
            raise KeyError
        else:
            self.d[k] = v