My class’ xor function is working as intended but when doing a^=b, I get ‘TypeError: unsupported operand type(s) for ^=: ‘NoneType’ and ‘Multiset.” Relevant code below:
def __xor__(self,o): d=Multiset() #subclass of dict for x in self|o: #for each item in both multisets m=abs((self[x] if x in self else 0) - (o[x] if x in o else 0)) #determines absolute difference of multiplicities of each element if m>0: d.add(x,m) #adds item x with multiplicity m to d return d def __ixor__(self,o): self=self^o
I have confirmed that a^b returns a Multiset and that setting a=a^b does not throw an error. I have tried commenting out the ixor definition as well as rewriting it as follows:
def __ixor__(self,o): buffer=self^o self=buffer
At this point, I’m just about out of ideas of what the problem could be.
The implementation of
__ixor__ method is wrong the assignment
self = buffer cannot be correctly assigned as it is not passed by reference.
In Python you can try perform an assignment like
self = buffer and so you’re actually rebinding the local variable
self to a new object (in this case, the
buffer object). However, this doesn’t modify the instance itself, and that’s why you’re not seeing the expected changes outside of the method.
So try to modify the attributes of the instance itself to reflect the changes made by the XOR operation. Here’s the corrected implementation:
def __ixor__(self, o): result = self ^ o # Calculate the XOR result using __xor__ self.clear() # Clear the current instance self.update(result) # Update the instance with the new result return self # Return the modified instance
In this implementation, we first calculate the XOR result using the
__xor__ method. Then, we clear the current instance using the
clear method (assuming
Multiset has this method) to remove all existing items. Finally, we update the instance with the new result using the
self at the end, we ensure that the method conforms to the expected behavior of an in-place operation and that the instance is properly modified.