On 4/16/2013 1:29 PM, Ethan Furman wrote:
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 <tjre...@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
'NoneType' is not a builtin name in builtins, which is precisely why you
accessed it the way you did ;-). From issue 17279 (for 3.3):
"Attached subclassable.py produces these lists:
Among named builtin classes, these cannot be subclassed:
bool, memoryview, range, slice,
Among types classes, these can be subclassed:
ModuleType, SimpleNamespace,"
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