Le 3 mars 2018 08:45, "Nick Coghlan" <ncogh...@gmail.com> a écrit :
On 3 March 2018 at 11:36, Greg Ewing <greg.ew...@canterbury.ac.nz> wrote: > 1. Name bindings local to an expression: > > roots = ([(-b-r)/(2*a), (-b+r)/(2*a)] where r = sqrt(b*b-4*a*c)) > > B. In an expression, surrounded by parentheses for > disambiguation. Bindings are visible only within the > parentheses. > I'll note that a significant benefit of this approach over the PEP 572 approach is that it would be amenable to a comprehension style scope-management solution: these expressions could create an implicitly nested function and immediately call it, just as 3.x comprehensions do. Adopting such an approach would *dramatically* lower the impact that hiding the bindings from the surrounding scope would have on the overall name resolution semantics. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/ As I said, allowing this syntax (whether with a new keyword like 'where' or reusing something like 'with' to write print(y with y = x+1)) in any expression (not only after a "for" in a comprehension list) is useful only if a local scope is created (otherwise, it would be the same as simple assignement but in reverse ordre). One could see : print(y with y = x+1) As a shortcut for : print(next(y for y in [ x+1 ])) The same as this : [y for x in range(5) with y = x+1] being a shortcut for : [y for x in range(5) for y in [ x+1 ]] As said, allowing both use cases would lead to two different ways to write : [y for x in range(5) with y = x+1] vs [y with y = x+1 for x in range(5)] But that is not really an issue, it's logically different (is the y a conclusion of the iteration or a hidden lambda in the expression?).
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