On 28 February 2018 at 15:18, Chris Angelico <ros...@gmail.com> wrote:
>> a = (2 as a) >> >> there is a temporary variable 'a', which gets assigned 2, and the SLNB is >> evaluated as 2, which should then get assigned back to the local variable >> 'a'. In other words, the final print from `f()` above should be 2, not 1. >> (Slightly different names would help avoid confusion when referencing >> different locations of the PEP.) > > Except that assignment is evaluated RHS before LHS as part of a single > statement. When Python goes to look up the name "a" to store it (as > the final step of the assignment), the SLNB is still active (it's > still the same statement - note that this is NOT expression-local), so > it uses the temporary. > > Honestly, though, it's like writing "a = a++" in C, and then being > confused by the result. Why are you using the same name in two > assignments? Normal code shouldn't do this. :) Eww. I can understand the logic here, but this sort of weird gotcha is precisely why people dislike C/C++ and prefer Python. I don't consider it a selling point that this proposal allows Python coders to make the sort of mistakes C coders have suffered from for years. Can you make sure that the PEP includes a section that covers weird behaviours like this as problems with the proposal? I'm happy if you just list them, or even say "while this is a potential issue, the author doesn't think it's a major problem". I just don't think it should be forgotten. Paul _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
