CODEWITHSUNDEEP
pythonset
Baron Yugovich
Baron Yugovich

Reputation: 4315

Python - can't define set of user-defined objects

I am getting the following error

    all_rots = set([rot1, rot2])
TypeError: an integer is required

My code is simply

rot1 = SimpleClass(mapping={1:1, 2:2})
rot2 = SimpleClass(mapping={2:2, 1:1})
all_rots = set([rot1, rot2])

(this is in unit test)

And the SimpleClass class is

class SimpleClass(object):
    def __init__(self, mapping):
        self._mapping = mapping


    @property
    def mapping(self):
        return self._mapping


    def __getitem__(self, key):
        return self.mapping[key]

    def __hash__(self):
        return sorted(list(self.mapping.iteritems()))

    def __eq__(self, other):
        if type(other) is type(self):
            return self.__dict__ == other.__dict__
        return False

Anyone has any idea why I cannot construct set of my objects?

Upvotes: 0

Views: 113

Answers (1)

Moses Koledoye
Moses Koledoye

Reputation: 78564

__hash__ should return an integer not a list.

You can create an immutable/hashable type from your sorted list (e.g. tuple) and return the hash of that:

def __hash__(self):
    return hash(tuple(sorted(self.mapping.items())))

rot1 = SimpleClass(mapping={1:1, 2:2})
rot2 = SimpleClass(mapping={2:2, 1:1})
all_rots = set([rot1, rot2])
print all_rots
# set([<Rotation object at 0x7f737e5ef210>])

Upvotes: 2

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