> On 23 Jan 2021, at 17:23, Avi Gross via Python-list <python-list@python.org> > wrote: > > I am wondering how hard it would be to let some generators be resettable?
That is generally thought to be a bad thing in OOD. Classes that reset are usually a code smell and often a source of bugs. Why not just assign a new generate into the variable that is used to access the generator. The avoids the need for the complications of reset logic. Barry > > I mean if you have a generator with initial conditions that change as it > progresses, could it cache away those initial conditions and upon some > signal, simply reset them? Objects of many kinds can be set up with say a > reinit() method. > > I am not saying Python needs such a language change for generators as in > many programs you could just recreate a new instance of a generator. But > there may be places where by the time the generator is used, the original is > not known. Or, there are places where you want to lengthen something to > match another by repeatedly copying the same sequence as many times as > needed. If a generator finishes, you want it to restart with the same > sequence until you stop asking. > > This is just a thought, not a request for such a feature. > > -----Original Message----- > From: Python-list <python-list-bounces+avigross=verizon....@python.org> On > Behalf Of ast > Sent: Saturday, January 23, 2021 2:54 AM > To: python-list@python.org > Subject: Re: list() strange behaviour > >> Le 20/12/2020 à 21:00, danilob a écrit : >> b = ((x[0] for x in a)) > > There is a useless pair of parenthesis > > b = (x[0] for x in a) > > b is a GENERATOR expression > > first list(b) calls next method on b repetedly until b is empty. > So it provides the "content" of b > > second list(b) provides nothing since b is empty (there is no reset on > generators) > > > > > -- > https://mail.python.org/mailman/listinfo/python-list > > -- > https://mail.python.org/mailman/listinfo/python-list -- https://mail.python.org/mailman/listinfo/python-list
