__slot__: what is it good for?

[Alexander Eisenhuth]

Hello out there,

- what is the reason, that __slots__ are introduced in python?

- I want to use slots to define a class where no attributes are added at
runtime. Is that a good idea to use slots for that?


Regards
Alexander

 

[James Mills]

Hello out there,

- what is the reason, that __slots__ are introduced in python?

- I want to use slots to define a class where no attributes are added at
runtime. Is that a good idea to use slots for that?

Here is the relevant documentation:'

http://docs.python.org/reference/datamodel.html#slots

 

[Peter Otten]

- what is the reason, that __slots__ are introduced in python?

When you have "many" instances of a class with a fixed set of attributes
__slots__ can save you some memory because it avoids the overhead for the
instance __dict__. Note that "many" means millions rather than thousands.
The best approach is to measure the memory footprint of your app with and
without __slots__ in the class you see as a good candidate and only use it
when you find a significant difference.

- I want to use slots to define a class where no attributes are added at
runtime. Is that a good idea to use slots for that?

No.

Peter

 

[Stephen Hansen]

If you don't want a class to have attributes added at runtime, the
Pythonic way to achieve that is to... simply add attributes at runtime.

Errr.

The Pythonic way to achieve that is to... simply NOT add attributes at
runtime.

I.e., choose to follow the rule you've decided on.

--

Stephen Hansen
... Also: Ixokai
... Mail: me+list/python (AT) ixokai (DOT) io
... Blog: http://meh.ixokai.io/


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[Terry Reedy]

The Pythonic way to achieve that is to... simply NOT add attributes at
runtime.

I.e., choose to follow the rule you've decided on.

Or add a __setattr__ method, but the above is easier.

 

[Stephen Hansen]

Or add a __setattr__ method, but the above is easier.

I'd sort of argue that adding a __setattr__ for that purpose is
un-Pythonic (as opposed to using __setattr__ for some functional purpose
and that restriction being a side-effect). Its possible to do it, sure;
but its also possible to use __slots__ to do so as well. But its bad
form in both cases.

But, that argument is largely Nit meeting Pick and having a fight about
which kettle is blacker.

--

Stephen Hansen
... Also: Ixokai
... Mail: me+list/python (AT) ixokai (DOT) io
... Blog: http://meh.ixokai.io/



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