https://mail.python.org/archives/list/python-ideas@python.org/message/XDRPPSQ2AVDCDDQQFXH772XGOK5Q7NE4/

void defaults handling.py

>>> import inspect, functools
>>>
>>> class Void:
...     pass
...
>>> def handle_defaults(f, undefined=Void):
...     sig = inspect.signature(f)
...     @functools.wraps(f)
...     def defaults_handled(*args, **kwargs):
...         bound = sig.bind(*args, **kwargs)
...         bound.apply_defaults()
...         for name, value in list(bound.arguments.items()):
...             if value is undefined:
...                 field = sig.parameters[name]
...                 if field.default is not inspect._empty:
...                     bound.arguments[name] = field.default
...         return f(*bound.args, **bound.kwargs)
...     return defaults_handled
...
>>>
>>> @handle_defaults
... def func(val="default"):
...     return val
...
>>> func(Void)
'default'
>>>
>>> def wrapper(val=Void):
...     return func(val)
...
>>>
>>> wrapper()
'default'