[Python-Dev] Shared ABCs for the IO implementation (original) (raw)

Guido van Rossum guido at python.org
Wed Feb 25 22:14:19 CET 2009

On Wed, Feb 25, 2009 at 1:03 PM, Antoine Pitrou <solipsis at pitrou.net> wrote:

Guido van Rossum <guido 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/)

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