[Python-Dev] PEP 572: Assignment Expressions

[Mike Miller]

Round 2 (Changed order, see below):

     1. with open(fn) as f:                   # current behavior
     2. with (open(fn) as f):                 # same

     3. with closing(urlopen(url)) as dl:     # current behavior
     5. with (closing(urlopen(url)) as dl):   # same

     4. with closing(urlopen(url) as dl):     # urlopener named early


On 2018-04-20 17:15, Chris Angelico wrote:
> The second and fifth could be special cased as either the same as
> first and third, or as SyntaxErrors. (But which?) 

If they are expressions, they should be the same once evaluated, no?

(I had a brief episode where I wrote that "as" was required with "with", instead 
of the CM object, sorry. :)

> The fourth one is very tricky. If 'expr as name' is allowed inside arbitrary
> expressions, why shouldn't it be allowed there?

Yes, they should be allowed there.

> The disconnect between viable syntax and useful statements is problematic here.

Number 4 appears to name the urlopener early.  Since closing() returns it as 
well, might it work anyway?

Might be missing something else, but #4 looks like a mistake with the layout of 
the parentheses, which can happen anywhere.  I don't get the sense it will 
happen often.

Cheers,
-Mike