What value should be passed to make a function use the default argument value?

[LaundroMat]

Antoon Pardon wrote:

> The problem is like the following.
>
> def f(var=1):
>   return var*2
>
> def g():
>   arg = None
>   try:
>     arg = Try_Processing() / 3 + 1
>   except Nothing_To_Process:
>     pass
>   if arg is None:
>     return f()
>   else:
>     return f(arg)
>
> Now in this case you could start by assigning arg the value 1 and
> eliminate the if test. However that only works if you know the
> default value for the argument. What he seems to be asking for
> is if there is an object, (let as call it Default), that would
> make code like:
>
>   def f(var=1):
>
> Equivallent to:
>
>   def f(var=Default)
>     if var is Default)
>       var = 1
>
> So that we could write the following without the need of the
> f's default value.
>
>   def g():
>     arg = Default
>   try:
>     arg = Try_Processing() / 3 + 1
>   except Nothing_To_Process:
>     pass
>   f(arg)
> 
> -- 
> Antoon Pardon

Exactly. Thanks for helping out.