__del__ for cdef classes

[Yury Selivanov]

Hi,

I'm working on an alternative implementation of asyncio event loop on Cython and libuv: https://github.com/1st1/uvloop

The results so far are extremely promising, I see 2-3.5x performance improvements in benchmarks: https://github.com/python/asyncio/issues/282#issuecomment-155957235

In uvloop I have to carefully track resources of libuv.  It would be nice if I had a way to define __del__ on a cdef class, so that I can resurrect it in some occasions -- I need it to follow PEP 442 semantics.  This way I can implement uvloop to behave closer to asyncio.

Is it possible to add __del__ methods for cdef classes?  Perhaps enabled only with special cython class decorator?  Only for Python > 3.4?

Thanks,

Yury

[Hai Nguyen]

You can try yourself by adding __del__ method. A dummy example here: https://github.com/Amber-MD/pytraj/blob/master/pytraj/frame.pyx#L145-L146

Hai

 

Thanks,

Yury

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[Robert Bradshaw]

You should look at __dealloc__.

[Stefan Behnel]

Robert Bradshaw schrieb am 25.11.2015 um 20:47:

> On Wed, Nov 25, 2015 at 9:44 AM, Yury Selivanov wrote:
>> I'm working on an alternative implementation of asyncio event loop on Cython
>> and libuv: https://github.com/1st1/uvloop
>>
>> The results so far are extremely promising, I see 2-3.5x performance
>> improvements in benchmarks:
>> https://github.com/python/asyncio/issues/282#issuecomment-155957235
>>
>> In uvloop I have to carefully track resources of libuv. It would be nice if
>> I had a way to define __del__ on a cdef class, so that I can resurrect it in
>> some occasions -- I need it to follow PEP 442 semantics. This way I can
>> implement uvloop to behave closer to asyncio.
>>
>> Is it possible to add __del__ methods for cdef classes? Perhaps enabled
>> only with special cython class decorator? Only for Python > 3.4?
>

> You should look at __dealloc__.

I don't think __dealloc__ is a good place to try to resurrect an object. It
might already be unusable at that point (GC cycle breaking, subclass
cleanups, ...).

Yury, could you give us an idea of the concrete problem you are trying to
solve? Why would your objects need to be resurrected?

"tp_del" is not currently a supported slot in Cython, but could be added.
See TypeSlots.py.

Stefan

[Robert Bradshaw]

On Wed, Nov 25, 2015 at 1:06 PM, Stefan Behnel <stef...@behnel.de> wrote:
> Robert Bradshaw schrieb am 25.11.2015 um 20:47:
>> On Wed, Nov 25, 2015 at 9:44 AM, Yury Selivanov wrote:
>>> I'm working on an alternative implementation of asyncio event loop on Cython
>>> and libuv: https://github.com/1st1/uvloop
>>>
>>> The results so far are extremely promising, I see 2-3.5x performance
>>> improvements in benchmarks:
>>> https://github.com/python/asyncio/issues/282#issuecomment-155957235
>>>
>>> In uvloop I have to carefully track resources of libuv. It would be nice if
>>> I had a way to define __del__ on a cdef class, so that I can resurrect it in
>>> some occasions -- I need it to follow PEP 442 semantics. This way I can
>>> implement uvloop to behave closer to asyncio.
>>>
>>> Is it possible to add __del__ methods for cdef classes? Perhaps enabled
>>> only with special cython class decorator? Only for Python > 3.4?
>>
>> You should look at __dealloc__.
>
> I don't think __dealloc__ is a good place to try to resurrect an object. It
> might already be unusable at that point (GC cycle breaking, subclass
> cleanups, ...).

Oh, missed the "resurrect" part.

> Yury, could you give us an idea of the concrete problem you are trying to
> solve? Why would your objects need to be resurrected?

+1

> "tp_del" is not currently a supported slot in Cython, but could be added.
> See TypeSlots.py.
>
> Stefan
>