On 29/05/15 06:48 PM, Alex Mohr wrote:
> On 5/29/2015 7:28 AM, Stefan Seefeld wrote:
>> Python's copy module allows for objects to be copied. The protocol for
>> this will look up special method __copy__. It seems to me that this
>> would trivially work for C++ objects providing a copy-constructor.
>> However, the copy-constructor isn't automatically bound to __copy__.
>> While I can certainly add that in user-code, I wonder why this isn't
>> done by Boost.Python itself.
>> Does anyone know the reasons for this ? Would it seem useful to add that
>> feature ?
>
> The __copy__ method's intended semantics are to produce a "shallow"
> copy while the __deepcopy__ method is meant to produce a "deep" copy.
> Given a C++ class with a copy ctor, it's hard to know which is more
> appropriate. For instance, copying a shared_ptr<T> is like a
> "shallow" copy but copying a vector<pair<int, float>> is like a deep
> copy. On the other hand copying a vector<shared_ptr<T>> is more like
> a shallow copy.
>
> I wouldn't mind an opt-in convenience utility that adds a __copy__ or
> __deepcopy__ method, but given the semantic subtlety, I think trying
> to do it automatically is dicey.
That's a fair point.
> Also, adding a feature to do it automatically could potentially
> interfere with existing binding code that manually provides
> __copy__/__deepcopy__ methods.
True, but that could be mitigated by always letting an explicit addition
override the default.
Stefan
--
...ich hab' noch einen Koffer in Berlin...
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