[Python-Dev] [Python-checkins] cpython: asyncio.events: Use __slots__ in Handle and TimerHandle

[Guido van Rossum]

On Wed, Feb 12, 2014 at 3:10 PM, Ethan Furman <ethan at stoneleaf.us> wrote:

> On 02/12/2014 02:02 PM, yury.selivanov wrote:
>
>> http://hg.python.org/cpython/rev/920304e1f36b
>> changeset:   89175:920304e1f36b
>> user:        Yury Selivanov <yselivanov at sprymix.com>
>> date:        Wed Feb 12 17:01:52 2014 -0500
>> summary:
>>    asyncio.events: Use __slots__ in Handle and TimerHandle
>>
>> files:
>>    Lib/asyncio/events.py |  4 ++++
>>    1 files changed, 4 insertions(+), 0 deletions(-)
>>
>>
>> diff --git a/Lib/asyncio/events.py b/Lib/asyncio/events.py
>> --- a/Lib/asyncio/events.py
>> +++ b/Lib/asyncio/events.py
>> @@ -19,6 +19,8 @@
>>   class Handle:
>>       """Object returned by callback registration methods."""
>>
>> +    __slots__ = ['_callback', '_args', '_cancelled']
>> +
>>       def __init__(self, callback, args):
>>           assert not isinstance(callback, Handle), 'A Handle is not a
>> callback'
>>           self._callback = callback
>> @@ -46,6 +48,8 @@
>>   class TimerHandle(Handle):
>>       """Object returned by timed callback registration methods."""
>>
>> +    __slots__ = ['_when']
>> +
>>       def __init__(self, when, callback, args):
>>           assert when is not None
>>           super().__init__(callback, args)
>>
>
> Apologies up front if these are stupid questions, but:
>
> Why __slots__?  Are we going to have so many of these things that memory
> is an issue
>

There's one of these created for every callback -- which includes every
time 'yield from' blocks for a Future. The savings are primarily in
allocation cost (no dicts to allocate).


> The asserts in the code -- those are not for checking user input, correct?
>

Yeah, this class is never instantiated directly by the user.

-- 
--Guido van Rossum (python.org/~guido)
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