Idiom gone, or did it really ever exist? () is ()

[Steve Purcell]

Delaney, Timothy wrote:
> > The convention is to use 'None' for this purpose. 'None' 
> > never changes, so
> > 'argument is None' will work correctly for you.
> 
> This will not actually work for the purpose though. The idea is to
> distinguish between whether a parameter was passed, or whether the default
> parameter is being used. Note: I've never tried this myself ...
> 
> If you have a default of None, it is impossible to determine this if the
> user passes None - because it will be the same instance of None in almost
> all cases.


Agreed. I'm just saying that this *is* the convention, not that replacing
the magic tuple values with None will work without further changes.

Given

   def foo(bar=None):
      ...

I think it's reasonable that

   foo()

and

   foo(None)

do the same thing.

Why prevent people from explicitly calling your function in the default way?

-Steve

-- 
Steve Purcell, Pythangelist
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