Get item from set python-CodePudding

I have a set which contains objects which I have the __eq__ and __hash__ functions defined for.

I would like to be able to check if an object with the same hash is in the set and if it is in the set to return the object from the set as I need the reference to the object.

class SetObject():
    def __init__(
        self,
        a: int,
        b: int,
        c: int
    ):
        self.a = a
        self.b = b
        self.c = c

    def __repr__(self):
        return f"SetObject ({self.a} {self.b} {self.c}) (id: {id(self)}"

    def __eq__(self, other):
        return isinstance(other, SetObject) \
               and self.__hash__() == other.__hash__()

    def __hash__(self):
        # Hash only depends on a, b
        return hash(
            (self.a,self.b)
        )

x = SetObject(1,2,3)
y = SetObject(4,5,6)

object_set = set([x,y])

print(f"{object_set=}")

z = SetObject(1,2,7)
print(f"{z=}")
if z in object_set:
    print("Is in set")
    # Get the object in set which is equal to z
    for element in object_set:
       if element == z:
           print(element)
           z = element

print(f"{z=}")

CodePudding user response：

Instead of using a set, use a dictionary where the keys and values are the same element. Then you can look use the value as a key and return the element.

x = SetObject(1,2,3)
y = SetObject(4,5,6)

object_set = dict([(x, x),(y, y)])

print(f"{object_set=}")

z = SetObject(1,2,7)
print(f"{z=}")
if z in object_set:
    print("Is in set")
    z = object_set[z]

print(f"{z=}")

If you want to simplify this, you could define a subclass of dict that automatically makes the values the same as the keys.