[Python-Dev] nodef (original) (raw)

Barry Warsaw barry at python.org
Thu May 24 02:40:35 CEST 2007

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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.

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