[Python-Dev] (name := expression) doesn't fit the narrative of PEP 20 (original) (raw)

Chris Barker chris.barker at noaa.gov
Fri Apr 27 14🔞14 EDT 2018

On Thu, Apr 26, 2018 at 1:33 PM, Tim Peters <tim.peters at gmail.com> wrote:

And that is a thing that you will have to explain to newbies when they encounter > it for the first time.

Sure. That doesn't frighten me, though. It's easy to explain what it does - although it may be hard to explain when it's desirable to use it.

I'm with Raymond here -- though I'm not sure "newbies" is quite right -- I've found that newbies fall into two camps: folks to whom programming comes naturally, and those that it doesn't (OK, it's a distribution, but a bimodal one). And folks that are struggling with programming can struggle even with simple assignment (name binding), particularly when you add even function local scope. So having one more way to do assignment WILL make it harder to teach, not because it's that hard, but because it's one more thing to learn.

But the fact is that as Python has evolved (particularly with the jump to py3) it has become less and less of a "scripting" language, and more of a "systems" language. And also harder to learn. Anyone remember CP4E? Python is not as good choice as a "newbie" language as it once was.

Adding := will move it a little bit more along the complexity path -- not much, and that's where Python has gone anyway, so as Tim said, no one's going to suffer either way this decision goes.

Hmm -- I wonder if a "pythonscript" will get forked off one day......

To judge from Stackoverflow volume, the single most misunderstood of

all Python operators - by far - is "is" -

You now, I think instructors like me are partly responsible. "is" is rarely useful outside of comparing to singletons. Yet I use it early in instruction to do checks on name binding and show things with mutablilty, etc.... which has the unfortunate side effect of making it seem like a more common operator than it is.

I've even had students write code like:

if x is 3:

and thanks to interning, it appears to work!

-CHB

--

Christopher Barker, Ph.D. Oceanographer

Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception

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