On Fri, Jun 15, 2018 at 6:54 PM, Chris Angelico <ros...@gmail.com> wrote: > On Sat, Jun 16, 2018 at 1:48 AM, Mikhail V <mikhail...@gmail.com> wrote: >> On Fri, Jun 15, 2018 at 5:51 AM, Michael Selik <m...@selik.org> wrote: >> >>> If you would like to prove the need for this operator, one piece of evidence >>> you can provide is a count of the number of times someone writes >>> "list.append" for an iterable vs "+=" and encloses a str or other type in a >>> throw-away list to effectively append. >> >> That's strange idea - there is no doubt that one would use >> list.append() and most probably >> it is the case statistically. >> So the question would be "what is wrong with list.append()?" >> And as said many times, there is nothing wrong, but a lot of people >> seem to want an in-place >> operator for this purpose. And I can understand this, because: >> >> 1. append() is _ubiquitous_ >> 2. in-place assignment form makes some emphasis on mutating, in >> contrast to method call. > > How so? You can write "x += 1" with integers, and that doesn't mutate; > but if you write "x.some_method()", doing nothing with the return > value, it's fairly obvious that it's going to have side effects, most > likely to mutate the object. Augmented assignment is no better than a > method at that. >
How it would be obvious unless you test it or already have learned by heart that x.some_method() is in-place? For a list variable you might expect it probably, and if you already aware of mutability, etc. It s just very uncommon to see standalone statements like: x.method() for me it came into habit to think that it lacks the left-hand part and =. Of course augmented assignment is not a panacea because it is limited only to one operation, and the appeal of the operator itself is under question. As for x+=1 it is implementation detail - historical idea of such operators was mutating, so at least visually its not like a returning expression. and I am not sure about x.method() form - was it meant to hint to the user about anything? It seemed to me so when I started to learn Python, but its not. _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
