Anyway, that is feasible via a decorator.
Since it can't be done the wya you are proposing as is, since
having a function as a default argument is valid Python
(and the function is not called) - and
having new syntax for this would be more cumbersome
than using a decorator, I think that closes the gap.
If such a decorator would be useful enough to cut it into the
stlib, is another question though - I'd probably find it occasionally
useful myself, but even so, I am +0 on this -
it is not like
```
if parameter is sentinel:
parameter = factory()
```
would be too much to type.
On a second thought - proper documenting and giving visibility
to a decorator like this could make it be used in patterns like
```
@factoryargs
def myfunction(a, b, c=list):
pass
```
and we could see a drop in the newcomers to Python
putting a `[]` as default argument.
Ok - I just convinced myself - I am +1 for such a decorator now.
Now, please, the S.O. link.
(that is me needing 2 more upvotes to round another 10K rep)