BrokenSet.sagews

class myObject():
    
    def __init__(self, v):
        self._value = v
        
    def __repr__(self):
        return str(self._value)
        
    def __eq__(self, other):
        return self._value == other._value
    
    def __hash__(self):
        return hash(self._value)

o = myObject(3)
o

3

s = set()
s.add(o)

s

set([3])

o._value = 4
s.add(o)
s

set([4, 4])

o._value = 3
s

set([3, 3])