On Tue, Mar 5, 2019 at 2:38 AM Inada Naoki <songofacandy@gmail.com> wrote:
On Tue, Mar 5, 2019 at 7:26 PM Steven D'Aprano <steve@pearwood.info> wrote:
> On Sat, Mar 02, 2019 at 01:47:37AM +0900, INADA Naoki wrote:
> > > If the keys are not strings, it currently works in CPython, but it may not work with other implementations, or future versions of CPython[2].
> >
> > I don't think so.  https://bugs.python.org/issue35105 and
> > https://mail.python.org/pipermail/python-dev/2018-October/155435.html
> > are about kwargs.  I think non string keys are allowed for {**d1,
> > **d2} by language.
> Is this documented somewhere?

It is not explicitly documented.  But unlike keyword argument,
dict display supported non-string keys from very old.

I believe {3: 4} is supported by Python language, not CPython
implementation behavior.


I'd like to remove all doubt: {**d1} needs to work regardless of the key type, as long as it's hashable  (d1 could be some mapping implemented without hashing, e.g. using a balanced tree, so that it could support unhashable keys).

If there's doubt about this anywhere, we could add an example to the docs and to the PEP.
--Guido van Rossum (python.org/~guido)