[Python-Dev] Shared ABCs for the IO implementation

[Antoine Pitrou]

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.

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".

Regards

Antoine.