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1. kwsp

   added

   docsDocumentation in the Doc dirDocumentation in the Doc dir

   on Dec 17, 2022
2. AlexWaygood commented on Dec 17, 2022

   

   AlexWaygood

   on Dec 17, 2022

   Last edited by AlexWaygood

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   The interactive REPL is always useful for discovering some of the answers to questions like this:

   >>> class Foo(int):
   ...   __slots__ = 'bar',
   ...   
   Traceback (most recent call last):
     File "<string>", line 1, in <module>
   TypeError: nonempty __slots__ not supported for subtype of 'int'
   >>> class Foo(str):
   ...   __slots__ = 'bar',
   ...
   >>>

   For your first question, we could possibly change the wording to

   • TypeError will be raised if nonempty slots are defined for a class derived from a “variable-length” built-in type such as int, bytes or tuple.

   For your second question: I don't know what's being referred to by "variable-length builtin types", so I agree that the wording there is a little opaque.
3. kumaraditya303 commented on Dec 17, 2022

   

   kumaraditya303

   on Dec 17, 2022

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   You can check if any type is variable length or not from python with <type>.__itemsize__ != 0. As for what it means, variable length is a memory layout when data follows the object pointer in single block like tuple in contrast to list which stores items in a separate memory block.
4. AlexWaygood commented on Dec 17, 2022

   

   AlexWaygood

   on Dec 17, 2022

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   As for what it means, variable length is a memory layout when data follows the object pointer in single block like tuple in contrast to list which stores items in a separate memory block.

   Is this definition given anywhere in the documentation? If so, we could maybe link to it from the __slots__ docs here.
5. AlexWaygood commented on Dec 17, 2022

   

   AlexWaygood

   on Dec 17, 2022

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   Looks like the best place to link to might be https://docs.python.org/3/c-api/typeobj.html#c.PyTypeObject.tp_itemsize. Hardly beginner-friendly, but probably better than no link at all (and I think it's good to keep the section on __slots__ in the datamodel terse).
6. kumaraditya303 commented on Dec 17, 2022

   

   kumaraditya303

   on Dec 17, 2022

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   Yeah, that's the best place I can find too.

   👍React with 👍1Reacted by Alex Waygood
7. kwsp commented on Mar 12, 2023

   

   kwsp

   on Mar 12, 2023

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   @kumaraditya303 I can't find __itemsize__ documented anywhere in the current documentation(docs search, duckduckgo). Could you please link any docs to __itemsize__? If its not available, could you tell me how you learnt about this, so we can add it to the docs?
8. kumaraditya303 commented on Mar 12, 2023

   

   kumaraditya303

   on Mar 12, 2023

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   I can't find itemsize documented anywhere in the current documentation(docs search, duckduckgo).

   It is not documented as it is an internal implementation detail.

   If its not available, could you tell me how you learnt about this, so we can add it to the docs?

   Just read the source code, in this case it is typeobject.c which contains the logic for type objects and memory management but it is not beginner friendly. I know all this because I work in these areas of interpreter often.

   👍React with 👍1Reacted by Taylor
9. kwsp

   added a commit that references this issue on Mar 12, 2023

   pythongh-100315: clarification to `__slots__` docs.

   ...

   6f6ba27
10. kwsp commented on Mar 12, 2023

    

    kwsp

    on Mar 12, 2023

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    Looks like the best place to link to might be https://docs.python.org/3/c-api/typeobj.html#c.PyTypeObject.tp_itemsize. Hardly beginner-friendly, but probably better than no link at all (and I think it's good to keep the section on slots in the datamodel terse).

    @AlexWaygood sounds good. I added this link to the docs in a PR.
11. AlexWaygood

    added a commit that references this issue on Mar 14, 2023

    gh-100315: clarification to `__slots__` docs. (#102621)

    ...

    88c262c
12. miss-islington

    added 2 commits that reference this issue on Mar 14, 2023

    pythongh-100315: clarification to `__slots__` docs. (pythonGH-102621)

    ...

    855a80f

    pythongh-100315: clarification to `__slots__` docs. (pythonGH-102621)

    ...

    c2d6fa1
13. kwsp

    closed this as completedon Mar 14, 2023
14. miss-islington

    added 2 commits that reference this issue on Mar 14, 2023

    gh-100315: clarification to `__slots__` docs. (GH-102621)

    ...

    2c015a6

    gh-100315: clarification to `__slots__` docs. (GH-102621)

    ...

    1f7eb8f
15. AlexWaygood commented on Mar 14, 2023

    

    AlexWaygood

    on Mar 14, 2023

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    Thanks for the PR @kwsp, and thanks for helping us figure this out @kumaraditya303! Fixed on 3.10-3.12.
16. carljm

    added a commit that references this issue on Mar 14, 2023

    Merge branch 'main' into inlinecomp2

    ...

    6c5f269
17. Fidget-Spinner

    added a commit that references this issue on Mar 27, 2023

    pythongh-100315: clarification to `__slots__` docs. (python#102621)

    ...

    9c61718
18. warsaw

    added a commit that references this issue on Apr 11, 2023

    pythongh-100315: clarification to `__slots__` docs. (python#102621)

    ...

    37736fc