Message7350

When special methods (e.g. __add__ or __sub__) return NotImplemented, then operations which internally use these methods should raise appropriate TypeError exceptions.
In CPython:
>>> class A:
... def __add__(self, other):
... return NotImplemented
... def __sub__(self, other):
... return NotImplemented
... 
>>> A() + A()
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'instance' and 'instance'
>>> A() - A()
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
TypeError: unsupported operand type(s) for -: 'instance' and 'instance' 
>>>
In Jython:
>>> class A:
... def __add__(self, other):
... return NotImplemented
... def __sub__(self, other):
... return NotImplemented
... 
>>> A() + A()
NotImplemented
>>> A() - A()
NotImplemented
>>>