Re: [Python-Dev] PEP 572: Now with 25% less reference implementation!

Maybe annotations should get a brief mention in the Rejected Ideas section, with your explanation here added. (And maybe my response.) On Thu, Apr 19, 2018 at 11:31 PM, Chris Angelico wrote:

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Hello Chris, and thank you for working on this PEP!

What do you think about using variable type hints with this syntax? I tried to search through python-dev and couldn't find a single post discussing that question. If I missed it somehow, could you please include its conclusions into

On Fri, Apr 20, 2018 at 2:45 PM, Dmitry Malinovsky wrote: the PEP?

I'm ignoring them for the sake of the PEP, because it'd complicate the grammar for little benefit. If someone wants to add an enhancement later, that's fine; but the proposal can stand without it, and with it, it'll make for even more noise in a line full of colons.

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For instance, as I understand now the parser will fail on this snippet:

while data: bytes := stream.read(): print("Received data:", data)

Do brackets help?

while (data: bytes := stream.read()): print("Received data:", data)

IIUC, in 3.7 It is invalid syntax to specify a type hint for a for loop item; should brackets help? Currently they don't:

Python 3.7.0b3+ (heads/3.7:7dcfd6c, Mar 30 2018, 21:30:34) [Clang 9.0.0 (clang-900.0.39.2)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> for (x: int) in [1,2,3]: File "<stdin>", line 1 for (x: int) in [1,2,3]: ^ SyntaxError: invalid syntax

And that's another good reason not to bother, at least for now. I'm not sure whether you can use a Py2-style type hint comment on a for loop, but if so, you should also be able to do it on a while loop or anything. Or, of course, you can just annotate the variable before the loop, if you want to.

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