Question

What’s a good way to implement a type safe dictionary in Python (3.2) – a dictionary that will only allow adding objects of a particular type to itself?

I myself have a simple solution: build a wrapper class around the dictionary with an ‘addItem’ method that does a type check assertion before adding the object. Looking to see if someone has something better.

Answer 1

I think you can extend the dictionary and overwrite the __setitem__ method

class MyDict(dict):
    def __setitem__(self, key, val):
        #Test for proper interface
        if val.pass_the_test:
            dict.__setitem__(self, key, val)
        else:
            raise SomeKindOfException()