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Date: Tue, 16 Apr 2013 10:29:18 -0700
From: Ethan Furman <ethan@stoneleaf.us>
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Subject: Re: The type/object distinction and possible synthesis of OOP and imperative programming languages
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On 04/16/2013 01:25 AM, Serhiy Storchaka wrote:
> On 16.04.13 07:46, Ian Kelly wrote:
>> On Mon, Apr 15, 2013 at 9:17 PM, Terry Jan Reedy <tjreedy@udel.edu> wrote:
>>> I will keep the above in mind if I write or review a patch. here are 4
>>> non-subclassable builtin classes. Two are already documented. Bool in one,
>>> forget which other. I believe it was recently decided to leave the other two
>>> as is given the absence of any practical use case.
>>
>> The four are bool, NoneType, slice and ellipsis, I believe.
>
> --> import builtins
> --> for n in dir(builtins):
> ...     if type(getattr(builtins, n)) is type:
> ...         try:
> ...             t = type(n, (getattr(builtins, n),), {})
> ...         except TypeError as e:
> ...             print(e)
> ...
> type 'bool' is not an acceptable base type
> type 'memoryview' is not an acceptable base type
> type 'range' is not an acceptable base type
> type 'slice' is not an acceptable base type

Well that bumps our count to five then:

--> NoneType = type(None)
--> NoneType
<class 'NoneType'>
--> class MoreNone(NoneType):
...   pass
...
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
TypeError: type 'NoneType' is not an acceptable base type

--
~Ethan~