Hmm, I actually have code that does something very similar to that. But it does not set it in `__init__` and instead uses it in a property where it is available. Tweaking your code,

```py
class DefaultBox(Generic[T]):
    def __init__(self, value: T | None = None):
        self._default_value = value
        self._value_set = False
   
     @property
     def value(self) -> T:
       if not self._value_set:
         self._value = self._default_value if self._default_value is not None else self.__orig_class__.__args__[0]()  

       return self._value
```

I think should work fine. Any reason initializing value afterwards is an issue? Or is the main goal that the original code is simpler then this lazy initialization workaround.