[Python-Dev] Language Summit notes

Guido van Rossum guido at python.org
Thu Apr 10 03:08:04 CEST 2014

To anyone who took notes at the language summit at PyCon today, even if you
took them just for yourself, would you mind posting them here? It would be
good to have some kind of (informal!) as soon as possible, before we
collectively forget. You won't be held responsible for correctness.

Here are some of my own recollections (I didn't take notes but I have a
decent memory):

- Packaging sucks, but we're improving, and we're actually doing better
than other dynamic languages.

- Kevin Modzelewski answered questions about Pyston, a new (very early
stage) Python VM based on the new LLVM JIT engine (which is much different
from what defeated Unladen Swallow). Alex Gaynor seemed unconcerned. :-)

- Jukka Lehtosalo gave a talk and answered questions about mypy, his design
and implementation of pragmatic type annotations (no new syntax required,
uses Python 3 function annotations). See mypy-lang.org. In response, Greg P
Smith pointed people to a similar project from Google,
https://github.com/google/pytypedecl, which has annotations in a separate
file (hence amenable to Python 2). Larry Hastings brought up that Argument
Clinic (a new way of specifying signatures for C extensions), released as
part of 3.4) encodes similar information in the docstring of C functions.

- Maybe this is should be the year when we start getting agreement on a
standard use of function annotations to specify argument and return types,
now that we seem to have a somewhat critical mass of experience with

- We should make an effort to publicize that we're NOT sunsetting Python
2.7 just yet; support will continue (hopefully with ample support from
distro vendors), and someone should update PEP 373. (Unclear what the new
EOL is but we should definitely rescind the currently published schedule.)

- We (I) still don't want to do a 2.8 release, and I don't want to
accelerate 3.5, but I do think we should make things better for people who
have to straddle Python 2 and 3 in a single codebase, by developing more
tools, and by security and possibly installer updates to 2.7 (PEP 466).

- Some suggestions that were made: PSF financial support for tool
development and/or porting, add more "-3" warnings to a future Python 2.7
release, additional 2to3 fixers to help convert Python-2-only code to
Python-2-and-3-single-source code, a separate linter, a sumo 2.7
distribution that includes all known backported-from-Python-3-stdlib
packages, adding ensure_pip to the 2.7.7 stdlib, and several more I forgot.
IIRC Glyph and Alex Gaynor are going to compile a list of pain points for
people. (I can't honestly say that I convinced Glyph and Alex and a few
others not to pine for 2.8, but I also honestly don't believe it will have
the effect that they expect. Nor do I believe any new feature we add to 3.5
can serve as a big enough carrot.)

- The recommended and least painful way to develop for Python 2 and 3 is
definitely to use a single source that runs under both without translation;
we no longer recommend auto-generating Python 3 compatible source code
using 2to3, for a variety of reasons. Several people attested that
single-source has worked well for them; Mercurial is using the 2to3
approach but they're not too happy with it.

- An argument for releasing something labeled 2.8 was made based on the
unavailability (current or future?) of Visual Studio 2008; the
uncomfortable alternative would be to switch to a newer compiler at some
2.7.x bugfix release, which would break extension modules compiled with for
2.7.0-2.7.6, and that would confuse and upset people.

- Apparently no restaurant in downtown Montreal takes reservations for a
group of 30 people to show up in one hour.

--Guido van Rossum (python.org/~guido)
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