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)
On Mon, 27 Jul 2020 at 20:42, Richard Damon
I have had a long standing unanswered question on on stackoverflow: is it possible to pass a function to a default parameter so that you could do in essence things like this.
def time_diff(target_time, curr_time= lambda : datetime.now() ): return curr_time - target_time
this would be an syntactical improvement over this style where you have if statement to initialize a missing parameter.
def time_diff(target_time, curr_time=None): if curr_time == None: curr_time = datetime.datetime.now() return curr_time - target_time I will point out that you CAN pass a function as the default value of a function parameter, and it means that the parameter will be bound to the function itself, so it becomes a callable (so doesn't help you in your case). But this does become an impediment to trying to define it this way, you need somehow to distinguish between the function itself being
On 7/27/20 10:01 AM, Peter Moore wrote: the default value, or some magically invocation of the function at each call.
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