Permanent objects?

[Bengt Richter]

On Thu, 26 Dec 2002 01:16:46 -0800, Erik Max Francis <max at alcyone.com> wrote:
[...]
>That's why when you hear talk about where people want to have optional
>arguments that could _also be None_, they talk about making _another_
>unique sentinel object, usually a private one to the class:
>
>	class C:
>	    _sentinel = object() # or whatever gets you a unique object
>	    def f(self, some, other=_sentinel):
>	        if other is _sentinel:
    Nit: you'll get an undefined global ref unless you use
	        if other is self._sentinel: # ( C._sentinel possible, but would depend on global C)
 
>	            ... # handle the case where other wasn't specified
>	        ... # handle the normal case, but None is a valid value
>
>The test with is (not ==) is important here, because I want to make sure
>it's _that object_, not merely an object that tests equal to it.  In
>fact you _don't_ want someone pretending

Regards,
Bengt Richter