1. It aligns with existing syntax in list comprehensions and generator expressions. 2. In probably majority of cases it would be more readable to me; "iterate over iterable for items meeting condition:". 3. Could it be easier to optimize an explicit filter expression to improve iteration performance?
On Wed, 2022-03-02 at 13:37 +1100, Steven D'Aprano wrote: > On Wed, Mar 02, 2022 at 02:28:33AM +0100, Svein Seldal wrote: > > > for x in y if x in c: > > some_op(x) > > What does this new syntax give us that we don't already have with > this? > > for x in y > if x in c: > some_op(x) > > or the other multiple ways of writing the equivalent code? > > I see no new functionality here. Is the only advantage that you save > one > line and one indent level? Both are cheap. > > To be precise, one extra line in something which is already a > multiline > statement is essentially insignificant, and while an extra indent > level > *can* be important, if you have already used so many indents that it > becomes important, you probably should be refactoring your code. > > All I see here is adding to the complexity of the parser and the > language for no meaningful benefit. Its not even easier to read, it > crams more on one line which in real code with meaningful variable > names > and a meanigful condition starts to get a bit long: > > # this line desperately needs to be split over two lines > for student in students if mean(student.grade(subject) for > subject in student.get_subjects()) > 0.8): > ... > > When I write list comprehensions with an if condition, probably 90% > of > the time I end up moving the if condition to a second or even third > line > of the comprehension. I expect the same will apply here. > > To save one line for maybe 10% of my for...if constructs, I don't > think > it is worth the bother of adding yet another way to do it. > >
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