Simple custom object that can be used inside sets.

hashing.py

class Hashable:

    def __init__(self, arg):
        self.arg = arg

    def __hash__(self):
        return hash(self.arg)

    def __eq__(self, other):
        return self.__hash__() == other.__hash__()


class Unhashable:

    def __init__(self, arg):
        self.arg = arg

    def __eq__(self, other):
        return self.arg == other.arg


data = []
for i in [1, 1, 2, 2]:
    obj = Unhashable(i)

    if obj not in data:
        data.append(obj)

print([obj.arg for obj in data])


data = {Hashable(i):0 for i in [1, 1, 2, 2]}
print([obj.arg for obj in data])