function argument dependent on another function argument?

[andrew cooke]

>     sentinel = object()
>     ...
>
>     def foo(x, y=sentinel):
>       if y is sentinel:
>           y = self.a

it just struck me you could also do:

     def foo(self, x, *y_args)
       y = y_args[0] if y_args self.a

which more directly checks whether an argument was passed, but has the
downside of making the method signature less clear in the declaration.

andrew