[Python-Dev] Shared ABCs for the IO implementation

[Nick Coghlan]

Guido van Rossum wrote:
> On Wed, Feb 25, 2009 at 1:03 PM, Antoine Pitrou <solipsis at pitrou.net> wrote:
>> Guido van Rossum <guido <at> python.org> writes:
>>> Without a shared ABC you'd defeat the whole point of having ABCs.
>>>
>>> However, importing ABCs (which are defined in Python) from C code
>>> (especially such fundamental C code as the I/O library) is really
>>> subtle and best avoided.
>>>
>>> In io.py I solved this by having a Python class inherit from both the
>>> ABC (RawIOBase) and the implementation (_fileio._FileIO).
>> My plan (let's call it "the Operation") is to define the ABCs in Python by
>> deriving the C concrete base classes (that is, have io.XXXIOBase derive
>> _io.XXXIOBase). This way, by inheriting io.XXXIOBase, user code will benefit
>> both from ABC inheritance and fast C concrete implementations.
> 
> However that's hardly an ABC. You need to provide a path for someone
> who wants to implement the ABC without inheriting your implementation.

Don't they already have that through register()?

However, the other problem with setting up the inheritance as Antoine
suggests is that it makes it impossible to import a pure Python version
of the module. Once the Python code inherits from something provided
only by the C module then the C version isn't optional any more.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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