Re: Null reference

On 2003.11.26 10:19, renz@xxxxxxxxxxxxxxxx wrote:
> Well, there will be no error occurred, if == is not defined for class
> v.  None in (mod.v(1), None) returns 1.

That's because the default behavior is to compare identity.

> I thought it should not compare equality, instead it should compare  
> identity.

It does by default. But when you define an operator== (or either __eq__  
or __cmp__ in Python) you're explicitly specifying that you want to  
override that behavior. That's not SWIG-specific---look at the  
following pure Python.

> > > class Foo:
...     def __eq__(self,x):
...         if x is None:
...             raise Exception("ni!")
...
> > > None in [ Foo(), None ]
Traceback (most recent call last):
 File "<stdin>", line 1, in ?
 File "<stdin>", line 4, in __eq__
Exception: ni!
> > >

You can't blame Python for not disregarding what you tell it.

Cheers,
        Luigi
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