Terry Reedy wrote: > "Boris Borcic" <[EMAIL PROTECTED]> wrote in message > news:[EMAIL PROTECTED] > >> being transformed to profit from simplifications I expected sets to allow. >> There, itemwise augmented assigments in loops very naturally transform to >> wholesale augmented assignments without loops. Except for this wart. > > Your transformation amounted to switching from collection mutation to > object rebinding. In Python, that is a crucial difference.
Ok, that is a crucial difference. The question becomes : is that difference in the case of augmented assignment maintained for practical or for purity aka ideological reasons ? > That the > mutation and rebinding were both done with augmented assignments is not > terribly important except as this masks the difference. When *you* read > your code, you know that you will only call the inner function with a > mutable collection object, so you know that the name will be rebound to the > same object after mutation, so you can think of the augmented assignment as > being the same as collection mutation. Not quite. When I read my code (and while I transform it) I know (as an invariant) that nowhere in my function do I initially bind a value to my variable, and I know that it can't be done with augmented assignments, and I know that no working code can /ever/ result from letting a function-local scope capture a name /just/ because it is the target of an augmented assignment. So, when despite this obvious certainty the compiler translates my code to something that can't possibly run while it happily translates x+=1 and x=x+1 to different bytecodes with no qualms about x possibly being bound to an immutable, well, I do feel victim of something like a hidden agenda. > > But the compiler does not know any such thing about the target of the > augmented assignment and must therefore treat the statement as an > assigment. It was a bug for a2 to do otherwise, even though the bug was > locally optimal for this particular usage. I must thank you for the effort of elaborating a polite and consistent explanation that was almost to the point and believable. Regards, Boris Borcic -- "On naît tous les mètres du même monde" _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
