On 09/08/2019 18:10, Brett Cannon wrote:
On Fri, Aug 9, 2019 at 9:03 AM Peter O'Connor <peter.ed.ocon...@gmail.com> wrote:Alright hear me out here: I've often found that it would be useful for the following type of expression to be condensed to a one-liner: def running_average(x_seq): averages = [] avg = 0 for t, x in enumerate(x_seq): avg = avg*t/(t+1) + x/(t+1) averages.append(avg) return averages Because really, there's only one line doing the heavy lifting here, the rest is kind of boilerplate.But it's boilerplate that communicates the starting state of your loop which is useful to know and to have be very clearly communicated.
+1. The intent and operation of your code is clear. Win.
Then I learned about the beautiful and terrible "for x in [value]": def running_average(x_seq): return [avg for avg in [0] for t, x in enumerate(x_seq) for avg in [avg*t/(t+1) + x/(t+1)]] Many people find this objectionable because it looks like there are 3 for loops, but really there's only one: loops 0 and 2 are actually assignments.
I find it objectionable because it's unreadable. I would reject this in a code review as "too clever for its own good," therefore unnecessarily hard to maintain.
**My Proposal** What if we just officially bless this "using for as a temporary assignment" arrangement, and allow "for x=value" to mean "assign within the scope of this for". It would be identical to "for x in [value]", just more readable. The running average function would then be: def running_average(x_seq): return [avg for avg=0 for t, x in enumerate(x_seq) for avg = avg * t/(t+1) + x / (t+1)]I personally don't find that more readable then the unrolled version you're trying to avoid. And based on the amount of grief we got for the walrus operator I wouldn't expect much uptake on this as being considered more readable by others either. (And remember that "Readability counts").
Agreed. -- Rhodri James *-* Kynesim Ltd _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/MO4G7T7H7BPWI2KLWDYQJQ7B7XEHJO2J/ Code of Conduct: http://python.org/psf/codeofconduct/
