[Python-Dev] nodef

[Barry Warsaw]

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On May 23, 2007, at 8:08 PM, Martin Blais wrote:

> I often have the need for a generic object to use as the default value
> for a function parameter, where 'None' is a valid value for the
> parameter.

I do the same thing for 'get' calls, where None is a legal return  
value.  I often call this unique object 'missing', e.g.

missing = object()
if some_dict.get('foo', missing) is missing:
     # It's missing

I like the way that reads.  Still, I'm -1 on adding something like  
this to built-ins because any built-in could potentially be a value  
in a mapping or a default argument.  Have some super-secret module  
global instantiated just for the purpose prevents that.

- -Barry

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