#12826: Use __slots__ for some simple objects.
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Reporter: sebastian_noack | Owner: nobody
Status: new | Milestone:
Component: Uncategorized | Version:
Resolution: | Keywords:
Stage: Design decision needed | Has_patch: 1
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by sebastian_noack):
I agree that {{{__slots__}}} might be confusing to the user and restrict
the flexibility of python. But for simple objects as those affected by my
patch, this is no problem, because of the way they are used is not a
problem with {{{__slots__}}}. So user's of django do not have to take care
about it. But they care about django's performance. And other frameworks
(e.g. jinja2) are using {{{__slots__}}} for some classes to improve
performance.
However, I have written a benchmark (see attachment). The result below,
shows that for PyPy there is even a bigger speed win as for CPython, when
using {{{__slots__}}}. I have done the benchmark on version 2.4 (which is
equivalent to PyPy 1.0) and 2.6 of CPython. The speed gain for Python 2.4
and 2.6 is similar. For CPython there is no difference in speed when the
attributes defined by {{{__slots__}}} are not set. But usually they are
set in the {{{__init__}}} method and in this case, classes using
{{{__slots__}}} are always faster. But note, if {{{__slots__}}} is defined
the object's {{{__dict__}}} is not created and in addition to the speed
gain the main advantage is that it needs less memory.
{{{
$ pypy --version
2.4.1 (pypy 1.0.0 build 55235)
$ pypy benchmark.py
| Avg. | Min. | Max.
--------------------+-------+-------+------
WithSlots | 0.136 | 0.116 | 0.152
--------------------+-------+-------+------
WithSlotsAndCtor | 0.220 | 0.215 | 0.229
--------------------+-------+-------+------
WithoutSlots | 0.153 | 0.142 | 0.176
--------------------+-------+-------+------
WithoutSlotsAndCtor | 0.287 | 0.276 | 0.304
$ python2.4 benchmark.py
| Avg. | Min. | Max.
--------------------+-------+-------+------
WithSlots | 0.021 | 0.018 | 0.025
--------------------+-------+-------+------
WithSlotsAndCtor | 0.093 | 0.090 | 0.101
--------------------+-------+-------+------
WithoutSlots | 0.021 | 0.020 | 0.021
--------------------+-------+-------+------
WithoutSlotsAndCtor | 0.107 | 0.102 | 0.113
$ python2.6 benchmark.py
| Avg. | Min. | Max.
--------------------+-------+-------+------
WithSlots | 0.026 | 0.024 | 0.028
--------------------+-------+-------+------
WithSlotsAndCtor | 0.092 | 0.089 | 0.093
--------------------+-------+-------+------
WithoutSlots | 0.026 | 0.025 | 0.028
--------------------+-------+-------+------
WithoutSlotsAndCtor | 0.113 | 0.107 | 0.125
}}}
--
Ticket URL: <http://code.djangoproject.com/ticket/12826#comment:2>
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