On Wed, Feb 25, 2009 at 1:03 PM, Antoine Pitrou <solipsis@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.
In turn, the concrete implementations in _pyio (the Python version) would register() those ABCs. The reason I think the Python implementations shouldn't be involved in the default inheritance tree is that we don't want user classes to inherit a __del__ method.
All this is assuming I haven't made any logic error. Otherwise, I'll have to launch "the new Operation".
-- --Guido van Rossum (home page: http://www.python.org/~guido/)