I believe this is a rebirth of a request that has come up many times before, which is to have something like javascript's `undefined` where it means "use the default value" if passed to a function that has a default value or "value not provided" (slightly different to "None").
def foo(x, y=1): ... return x, y
foo(undefined, undefined) undefined, 1
The idea being that wrapper functions don't need to then know what the default is for the function they wrap: def outermost_wrapper(b, c=undefined): return inner_wrapper(5, b, c) def inner_wrapper(a, b=undefined, c=undefined): return func(a, b, c) def func(a=1, b=2, c=3): return a*b*c "undefined" would either have to be an alias for "None" everywhere _except_ function signatures, or be only allowed in function signatures and have special handling. It opens up a can of worms in javascript but has its uses.