python - construire un objet qui peut être mappé ou un emballé - Stack Overflow

So I have this (of course the true thing is more complicated) :

class test(object):
    i = -1

    def keys(self):
        return ["a", "b"]

    def __getitem__(self, item):
        return {"a": 0, "b": 1}[item]

    def __len__(self):
        return 2

    def __contains__(self, item):
        if item in ["a", "b"]:
            return True
        return False

    def __iter__(self):
        return self

    def next(self):
        self.i += 1
        if self.i > 1:
            raise StopIteration()

        return ["a", "b"][self.i]

What I want to do is this (again the true thing is more complex):

> t = test()
> dict(t)
 {'a': 0, 'b': 1}
> dict(**t) 
 {'a': 0, 'b': 1}

This work perfectly, but fail to work if I define the class as a subclass of a dict, and this is what I want, I want my object to behave like a dict with some hidden tricks under knees (and again sure it makes more sense in the real code):

class test(dict):
     .... same code here ....

In this case the dict(t) and dict(**t) will return an empty dictionary {}, but [k for k in t] will return ['a','b'].

What do I miss ? It seems that I do need to redeclare some dict function, I though that __getitem__, __iter__, __len__, __contains__ and keys method was enough to do the trick. I tried to redeclare iterkeys, itervalues, copy, get, etc, but nothing seems to work.

Thanks.

So I have this (of course the true thing is more complicated) :

class test(object):
    i = -1

    def keys(self):
        return ["a", "b"]

    def __getitem__(self, item):
        return {"a": 0, "b": 1}[item]

    def __len__(self):
        return 2

    def __contains__(self, item):
        if item in ["a", "b"]:
            return True
        return False

    def __iter__(self):
        return self

    def next(self):
        self.i += 1
        if self.i > 1:
            raise StopIteration()

        return ["a", "b"][self.i]

What I want to do is this (again the true thing is more complex):

> t = test()
> dict(t)
 {'a': 0, 'b': 1}
> dict(**t) 
 {'a': 0, 'b': 1}

This work perfectly, but fail to work if I define the class as a subclass of a dict, and this is what I want, I want my object to behave like a dict with some hidden tricks under knees (and again sure it makes more sense in the real code):

class test(dict):
     .... same code here ....

In this case the dict(t) and dict(**t) will return an empty dictionary {}, but [k for k in t] will return ['a','b'].

What do I miss ? It seems that I do need to redeclare some dict function, I though that __getitem__, __iter__, __len__, __contains__ and keys method was enough to do the trick. I tried to redeclare iterkeys, itervalues, copy, get, etc, but nothing seems to work.

Thanks.

Source