On Thu, Mar 1, 2018 at 10:35 PM, Chris Angelico <ros...@gmail.com> wrote: > On Fri, Mar 2, 2018 at 4:16 PM, Ian Kelly <ian.g.ke...@gmail.com> wrote: >> On Wed, Feb 28, 2018 at 8:00 PM, Chris Angelico <ros...@gmail.com> wrote: >>> Not off hand, but I can provide an EXTREMELY real-world example of a >>> fairly tight loop: exceptions. An exception has a reference to the >>> local variables it came from, and those locals may well include the >>> exception itself: >>> >>> try: >>> 1/0 >>> except Exception as e: >>> print(e) >>> >>> The ZeroDivisionError has a reference to the locals, and 'e' in the >>> locals refers to that very exception object. >> >> The problem with this example of course is that the variable 'e' is >> scoped to the except block and automatically del'ed when it exits. > > Or, to be more accurate: The language design acknowledges that this > reference cycle is a fundamental problem, and the *solution* is that > there's an implicit "e = None; del e" at the end of the except block. > > You can easily defeat that protection with "except Exception as ee: e > = ee", if you want to demonstrate the cycle.
Yes, but how often does this happen in practice? This situation was billed as "an EXTREMELY real-world example". In the real world, most of the time when you have an exception, you log it or handle it, and then you discard it. -- https://mail.python.org/mailman/listinfo/python-list
