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

[Antoon Pardon]

On 2006-10-03, LaundroMat <Laundro at gmail.com> wrote:
> Suppose I have this function:
>
> def f(var=1):
> return var*2
>
> What value do I have to pass to f() if I want it to evaluate var to 1?
> I know that f() will return 2, but what if I absolutely want to pass a
> value to f()? "None" doesn't seem to work..
>
> Thanks in advance.
>

I think the only general solution for your problem would be to
define a defaulter function. Something like the following:

  Default = object()

  def defaulter(f, *args):

    while args:
      if args[-1] is Default:
        args = args[:-1]
      else:
        break
    return f(*args)


The call:

  defaulter(f, arg1, arg2, Default, ..., Default)

would then be equivallent to:

  f(arg1, arg2)

Or in your case you would call:

  defaulter(f, Default)

-- 
Antoon Pardon