[Python-Dev] PEP 572: Assignment Expressions

[Guido van Rossum]

Please stop debating `<expr> as <name>`. Nobody is being swayed by anything
in this subthread. Let's move on.

On Sun, Apr 22, 2018 at 3:27 PM, Chris Angelico <rosuav at gmail.com> wrote:

> On Mon, Apr 23, 2018 at 8:20 AM, Mike Miller <python-dev at mgmiller.net>
> wrote:
> >
> > On 2018-04-22 14:33, Chris Angelico wrote:
> >>
> >> with open(fn) as f:
> >> with (open(fn) as f):
> >>
> >> These two do the same thing, but only because a file object's
> >> __enter__ returns self. So it's dangerous, because it WILL work... and
> >> people will get into the habit of parenthesizing to permit a 'with'
> >> statement to go across line breaks. And then they'll use a different
> >> context manager, like closing(), or a PsycoPG2 database connection (I
> >> think), where it returns something else. And it'll work, until they go
> >> over multiple lines, and then suddenly the semantics change.
> >
> >
> >
> > Why do you think folks will be rushing to parenthesize with statements
> when
> > it has always been a syntax error, there is years of code and docs that
> show
> > otherwise, no use cases, and will take years for 3.8 to trickle out?
>
> Because it's been requested a number of times as a way to allow a
> 'with' statement to go across lines without backslashes.
>
> If it becomes possible, it will be used.
>
> ChrisA
> _______________________________________________
> Python-Dev mailing list
> Python-Dev at python.org
> https://mail.python.org/mailman/listinfo/python-dev
> Unsubscribe: https://mail.python.org/mailman/options/python-dev/
> guido%40python.org
>



-- 
--Guido van Rossum (python.org/~guido)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-dev/attachments/20180422/f7dcfff7/attachment.html>