On 31/10/2021 08:05, Steven D'Aprano wrote:
On Tue, Oct 26, 2021 at 08:59:51AM +0100, Rob Cliffe via Python-ideas wrote:
And I don't understand what point you're making here. Yes, the walrus
operator can appear in various places, how is that relevant? You could write
def f(a := (b := c)):
which might be a tad confusing but would be unambiguous and legal, just as
def f(a = (b := c)):
is currently legal (I tested it). I don't see a clash.
If we have a choice between a dozen syntax variants that are not
confusing, and one which is confusing, why would we prefer to pick the
one that is confusing over any of the others?
"confusing" is a subjective term. So is "evocative" - see below.
Consider the colon. Currently it has various meanings, including
- introducing an indented suite
- slicing
- dictionary displays
- use in annotations (I think)
and others I don't remember right now, probably half-a-dozen in all.
But we don't get confused when we (very commonly) see it used in 2
different ways in the same line:
if not sys.argv[1:]: # 1st example I came across in the stdlib
nor would we if it were used in 3 or more ways in the same line. Because
we're familiar with it.
Now
def f(a := (b := c)):
might be a tad confusing AT FIRST, until we got used to it. But
- this would be very uncommon, and IMO in most cases bad code
- there would never be *more* than 2 meanings for `:=` in the same
line, because there would only BE two meanings for it. (I refrain from
calling it `the walrus operator` here because the first one would be
better called `the late default assignment operator` or some such.)
Meanwhile, BEFORE we got used to it, I maintain that the similarity of
`:=` to the early default assignment operator, viz. `=`, not to mention
to the real walrus operator, is definitely evocative of some sort of
(default?) value being given (somehow, sometime) to the parameter.
Whereas adding (somewhere) a symbol such as '@' or '?' conveys nothing
to me. YMMV, naturally. And of course it keeps that symbol free for
another future use.
Best wishes
Rob Cliffe
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