On Tue, Nov 27, 2018 at 08:26:04PM -0500, Avi Gross wrote: > Ivo, You've replied to the wrong mailing list. Ivo wrote to Python-List, not Tutor.
But now that you've raised the issue... [Ivo asked] > Why: > if (match := pattern.search(data)) is not None: > # Do something with match > > What is wrong with: > if match = pattern.search(data) is not None: > # Do something with match > > Assignment expression or assignment statement, it's an assignment, right? > It is very clear to everyone that it's an assignment! Can't it all just be a > "="? It seems that Ivo didn't read the PEP because that is discussed: https://www.python.org/dev/peps/pep-0572/#id32 Despite Ivo's statement that it is "clear to everyone", the problem is that whenever you see an assignment x=y in an assignment, there's no obvious way of telling whether they meant assignment or it was a mistyped equality test x==y. So it is not clear at all. In C, this confusion between = and == is a frequent source of serious bugs, including one attempt at inserting a back-door into the Linux kernel: https://freedom-to-tinker.com/2013/10/09/the-linux-backdoor-attempt-of-2003/ https://lwn.net/Articles/57135/ Requiring the colon x:=y makes it less likely to mess up the assignment or comparison. -- Steve _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
