list() strange behaviour

[Avi Gross]

I am wondering how hard it would be to let some generators be resettable?

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.net at python.org> On
Behalf Of ast
Sent: Saturday, January 23, 2021 2:54 AM
To: python-list at 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)




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