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Re: NoneType and new instances

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  Re: NoneType and new instances Ian Kelly <ian.g.kelly@gmail.com> - 2011-07-28 11:12 -0600
    Re: NoneType and new instances Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-07-29 11:20 +1000

#10466 — Re: NoneType and new instances

On Thu, Jul 28, 2011 at 9:39 AM, Ethan Furman <ethan@stoneleaf.us> wrote:
> Why is NoneType unable to produce a None instance?  I realise that None is a
> singleton, but so are True and False, and bool is able to handle returning
> them:

The bool constructor works (actually just returns one of the existing
singletons) so that you can do things like this:

truth_value = bool(x + 5)
return my_dict[truth_value]

Why would you ever need to instantiate NoneType?

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#10494

Ian Kelly wrote:

> Why would you ever need to instantiate NoneType?


Well, you probably wouldn't deliberately, but if you have code like this:


types = [type(x) for x in list_of_objects]
# later on...
for t in types:
    instance = t()
    do_something_with(instance)


it would be nice if it didn't explode when list_of_objects contains None.


-- 
Steven

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