On Fri, Oct 14, 2016 at 06:23:32PM +1300, Greg Ewing wrote:
To maintain the identity
list(*x for x in y) == [*x for x in y]
it would be necessary for the *x in (*x for x in y) to expand to "yield from x".
Oh man, you're not even trying to be persuasive any more. You're just assuming the result that you want, then declaring that it is "necessary". :-( I have a counter proposal: suppose *x is expanded to the string literal "Nope!". Then, given y = (1, 2, 3) (say): list(*x for x in y) gives ["Nope!", "Nope!", "Nope!"], and [*x for x in y] also gives ["Nope!", "Nope!", "Nope!"]. Thus the identity is kept, and your claim of "necessity" is disproven. We already know what *x should expand to: nearly everywhere else, *x is conceptually replaced by a comma-separated sequence of the items of x. That applies to function calls, sequence unpacking and list displays. The only exceptions I can think of are *args parameters in function parameter lists, and sequence packing on the left side of an assignment, both of which work in similar fashions. But not this proposal: it wouldn't work like either of the above, hence it would be yet another unrelated use of the * operator for some special meaning. -- Steve