On 10 Feb 2016, at 5:52 pm, Guido van Rossum <gu...@python.org> wrote:
>
> On Wed, Feb 10, 2016 at 1:11 AM, Phil Thompson
> <p...@riverbankcomputing.com> wrote:
>> I understand now. The documentation, as it stands, is correct and consistent
>> but (to me) the meaning of Optional is completely counter-intuitive. What
>> you suggest with str = ... is exactly what I need. Adding a section to the
>> docs describing that should clear up the confusion.
>
> I tried to add some clarity to the docs with this paragraph:
>
> Note that this is not the same concept as an optional argument,
> which is one that has a default. An optional argument with a
> default needn't use the ``Optional`` qualifier on its type
> annotation (although it is inferred if the default is ``None``).
> A mandatory argument may still have an ``Optional`` type if an
> explicit value of ``None`` is allowed.
>
> Should be live on docs.python.org with the next push (I don't recall
> the delay, at most a day IIRC).
That should do it, thanks. A followup question...
Is...
def foo(bar: str = Optional[str])
...valid? In other words, bar can be omitted, but if specified must be a str or
None?
Thanks,
Phil
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