NoneType and new instances
ben+python at benfinney.id.au
Thu Jul 28 23:46:38 CEST 2011
Ethan Furman <ethan at stoneleaf.us> writes:
> Why is NoneType unable to produce a None instance? I realise that None
> is a singleton
That answers your question. Because None is a singleton, the job of its
type is to make sure there are no other instances.
> but so are True and False, and bool is able to handle returning them:
Well, they don't meet the definition of a singleton, because there are
two instances of ‘bool’ :-)
There may be code out there which depends on the fact that there once
was never a ‘bool’ type, or depends on the fact that bools are also
‘int’ instances, and it's been deemed not-worth-the-trouble to break
> This feels like a violation of 'Special cases aren't special enough to
> break the rules.'
In the case of ‘bool’, the rule was broken before being introduced.
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