On Thu, Feb 28, 2019 at 11:13 PM Rhodri James <rho...@kynesim.co.uk> wrote: > > On 27/02/2019 21:39, Roel Schroeven wrote: > > Rhodri James schreef op 27/02/2019 om 15:18: > > Aren't we overthinking this? > > > > I think it's pretty clear that a variable is never deleted before it > > goes out of scope. A quick search in the documentation points me to > > (https://docs.python.org/3/reference/datamodel.html#objects-values-and-types): > > > > > > "Objects are never explicitly destroyed; however, when they become > > unreachable they may be garbage-collected. An implementation is allowed > > to postpone garbage collection or omit it altogether — it is a matter of > > implementation quality how garbage collection is implemented, *as long > > as no objects are collected that are still reachable*." (emphasis mine) > > > > In the original example (without del), f is reachable everywhere in the > > function after the initial binding, so it can not be deleted. > > > > Comparisons with C on this point don't seem very relevant: C doesn't > > have destructors or garbage collection. I don't even see what the C > > equivalent for "del f" could be. You could perhaps compare with C++, > > where destructors are also not called before the object goes out of > > scope (a difference is that in C++ the destructor explicitly always is > > called at that moment). > > I think you're making the mistake of equating names ("variables") and > objects here. It is not clear to me that a name can't be removed from > the dictionary of locals before it goes out of scope, so long as it > doesn't get referred to again, just like C optimisers can note that a > local doesn't get used again and reclaim the storage. At that point the > object can become unreachable, and will in Marko's example. > > The equivalent to "del f" that you can't imagine is the optimiser at work. >
What if an exception gets raised at some point before the function has returned? The exception object will give full access to the function's locals. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
