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[Python-Dev] [RFC] Removing pure Python implementation of OrderedDict

alex goretoy agoretoy at gmail.com
Wed Sep 6 08:34:21 EDT 2017 
https://www.youtube.com/watch?v=pNe1wWeaHOU&list=PLYI8318YYdkCsZ7dsYV01n6TZhXA6Wf9i&index=1


On Wed, Sep 6, 2017 at 5:49 PM, INADA Naoki <songofacandy at gmail.com> wrote:
> OK, I stop worring about thread safety and other implementation
> detail behavior on edge cases.
>
> Thanks,
>
> INADA Naoki  <songofacandy at gmail.com>
>
>
> On Wed, Sep 6, 2017 at 7:40 PM, Paul Moore <p.f.moore at gmail.com> wrote:
>> On 6 September 2017 at 11:09, Antoine Pitrou <solipsis at pitrou.net> wrote:
>>> On Wed, 6 Sep 2017 11:26:52 +0900
>>> INADA Naoki <songofacandy at gmail.com> wrote:
>>>>
>>>> Like that, should we say "atomic & threadsafe __setitem__ for simple
>>>> key is implementation detail of CPython and PyPy.  We recommend
>>>> using mutex when using OrderedDict from multiple thread."?
>>>
>>> I think you may be overstating the importance of making OrderedDict
>>> thread-safe.  It's quite rare to be able to rely on the thread safety
>>> of a single structure, since most often your state is more complex than
>>> that and you have to use a lock anyway.
>>>
>>> The statu quo is that only experts rely on the thread-safety of list
>>> and dict, and they should be ready to reconsider if some day the
>>> guarantees change.
>>
>> Agreed. I wasn't even aware that list and dict were guaranteed
>> threadsafe (in the language reference). And even if they are, there's
>> going to be a lot of provisos that mean in practice you need to know
>> what you're doing to rely on that. Simple example:
>>
>>     mydict[the_value()] += 1
>>
>> isn't thread safe, no matter how thread safe dictionaries are.
>>
>> I don't have a strong opinion on making OrderedDict "guaranteed thread
>> safe" according to the language definition. But I'm pretty certain
>> that whether we do or not will make very little practical difference
>> to the vast majority of Python users.
>>
>> Paul
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