[Python-Dev] PEP 572: Assignment Expressions (original) (raw)

Chris Angelico rosuav at gmail.com
Sun Apr 22 18:27:42 EDT 2018

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

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