[Python-Dev] IO implementation: in C and Python? (original) (raw)

Terry Reedy tjreedy at udel.edu
Fri Feb 20 21:26:10 CET 2009

Guido van Rossum wrote:

On Fri, Feb 20, 2009 at 4:01 AM, Antoine Pitrou <solipsis at pitrou.net> wrote:

Georg Brandl <g.brandl gmx.net> writes:

I just hope everyone updates both versions when making changes to IO. My proposal is just organizational, it is neutral in terms of whether or not the Python version is correctly maintained. I worry that with your proposal people are once again going to import the pure Python version where they shouldn't. Maybe pyio.py would work though?

From a user perspective, continuity of 'import xyz' importing the currently best implementation is what is important, even if that switches back and forth.

We can hope that the IO lib semantics won't change too much in the future (although there is an IMO legitimate request for a setblocking() method: http://bugs.python.org/issue949667). On the other hand, I don't expect anyone to willingly use the Python version if the C version is available. Hoping that modules won't evolve is futile. The concern for divergence is real. Unit-testing both with the same tests might be the solution.

It seems to me that starting new features with a new test and prototyping in the Python version should mostly avoid the problem. Keeping the Python version allows non-C Pythoneers to contribute to such efforts. (As opposed to fixing a C-only bug.) If the Python version is ahead at the time of a release, the Python version could be reverted to being a master version that import the C version for most but not all functions.

tjr

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