[Python-Dev] PEP 572: Assignment Expressions

[Chris Barker]

On Thu, Apr 19, 2018 at 5:45 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:

> * for the while loop use case, I think my discussion with Tim about
> tuple unpacking shows that the loop-and-a-half construct won't be
> going anywhere, so users would still end up needing to learn both
> forms (even for new code)
>

well, yes, but I've always found while awkward in the common case -- and
wanted a better way (maybe an until?).

using:

while True:
   ...

for a loop with a clear testable termination criteria always felt clunky.

Anyone recall the "canonical" way to loop through the lines of a file
before we had the file iterator?

while True:
    line = fp.readline()
    if not line:
        break
    do_stuff_with(line)


This is in fact, the only compeling use case for this to me -- maybe we
could make a way to do an assign and test in a while loop enhancement just
for that?

And no, I have no idea what that would look like -- I'm mostly joking.

So -1 on this -- though I agree -- great PEP Chris!

And -1, not -0 because I think this really would add one more complication
to a language that used to be so simple, and still is (and should be) used
a first programming language. I teach a lot of newbies, and I'm realy not
l;ooking forward to one more way to do assignement. It starts simpel enough:

x = something

binds the name, "x" the the object, 'something' is bound to (or a literal)

Then we get into:
 - multiple assignment
 - tuple unpacking (oops, sequence unpacking),
 - augmented assignment
 - oh, that works different depending on whether the object is mutable

We don't need any more.

-CHB


-- 

Christopher Barker, Ph.D.
Oceanographer

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