[Python-Dev] Computed Goto dispatch for Python 2 (original) (raw)

Brett Cannon brett at python.org
Thu May 28 16:02:03 CEST 2015

On Thu, May 28, 2015 at 8:47 AM Raymond Hettinger < raymond.hettinger at gmail.com> wrote:

> On May 28, 2015, at 1:54 AM, Berker Peksağ <berker.peksag at gmail.com> wrote: > > * Performance improvements are not bug fixes Practicality beats purity here.

Recognize that a huge number of Python users will remain in the Python2.7

world for some time. We have a responsibility to the bulk of our users (my estimate is that adoption rate for Python 3 is under 2%).

Where does that number come from? I have not seen numbers less than 5% for the overall community adoption (and all of them are extremely rough and all skewed towards Python 2 for various technical reasons).

The computed goto patch makes substantial performance improvements. It is callous to deny the improvement to 2.7 users.

But you could argue that "Special cases aren't special enough to break the rules" and that's what we are proposing here by claiming Python 2.7 is a special case and thus we should accept a patch that is not a one-liner change to gain some performance in a bugfix release.

> * The patch doesn't make the migration process from Python 2 to Python 3 easier Sorry, that is a red-herring (an orthogonal issue). If you care about 2-to-3 migration, then start opposing proposals for API changes that increase the semantic difference between 2 and 3.

That's misdirection for Berker's point that the proposal at hand does not help with getting to people to Python 3 even though what is proposed is an enhancement and not a bugfix (since we are not fixing a performance regression). I had someone on Twitter earlier this month point out that Python 3 was slower than Python 2 on some benchmark and that was a reason they weren't switching. Doing this is not going to help make that case (although I think arguing about performance between 2 and 3 is misleading when I've seen other workloads win out in Python 3).

I'm -0 on this because I would like to stick to our policy of no enhancements in a bugfix release, but in the end it's Benjamin's call as 2.7 RM as to whether this is appropriate for 2.7.11. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20150528/0f432d9a/attachment.html>

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