On 23 November 2017 at 15:21, Paul Moore <p.f.mo...@gmail.com> wrote:
> On 23 November 2017 at 13:04, Ivan Levkivskyi <levkivs...@gmail.com> > wrote: > > Let us forget for a moment about other problems and focus on this one: > list > > comprehension is currently not equivalent to a for-loop. > > There are two options: > > - Fix this, i.e. make comprehension equivalent to a for-loop even in edge > > cases (Serhiy seems ready to do this) > > - Prohibit all cases when they are not equivalent > > > > I still prefer option one. But I see your point, option two is also an > > acceptable fix. > > Note that there were not so many situations when some code became > > SyntaxError later. > > I don't see why this particular case qualifies for such a radical > measure as > > an exception to syntactic rules, > > instead of just fixing it (sorry Nick :-) > > My main concern is that comprehension is not equivalent to a for loop > for a specific reason - the scope issue. Has anyone looked back at the > original discussions to confirm *why* a function was used? > > My recollection: > > >>> i = 1 > >>> a = [i for i in (1,2,3)] > >>> print(i) > 1 > > Serihy's approach (and your described expansion) would have print(i) > return NameError. > Absolutely no, it will still print 1. The internal implementation will use unique ids internally (see https://bugs.python.org/issue10544 for details). -- Ivan
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