[Python-Dev] Python 2.x and 3.x use survey, 2014 edition (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Sun Dec 14 01:14:42 CET 2014

On 13 Dec 2014 05:19, "Petr Viktorin" <encukou at gmail.com> wrote:

Also keep in mind that not all Python libraries are on PyPI. For non-Python projects with Python bindings (think video players, OpenCV, systemd, Samba), distribution via PyPI doesn't make much sense. And since the Python bindings are usually second-class citizens, the porting doesn't have a high priority. If anyone is wondering why their favorite Linux distribution is stuck with Python 2 – well, I can only speak for Fedora, but nowadays most of what's left are CPython bindings. No pylint --py3k or 2to3 will help there...

That's a good point. I actually think https://docs.python.org/3/howto/cporting.html#cporting-howto is actually in a worse state than the state the Python level porting guide was in until Brett's latest round of updates, as it covers the underlying technical details of the incompatibilities moreso than the available tools and recommended processes for executing a migration.

For example, replacing a handcrafted Python extension with a normal C library plus cffi, Cython or SWIG generated Python bindings can deliver both an easier to maintain extension and Python 3 compatibility.

Similarly, converting an extension from C to Cython outright (without a separate C library) can provide both benefits.

It's mainly when converting to one of those isn't desirable and/or feasible that you really need to worry about C API level porting.

For that, tools like Dave Malcolm's static CPython extension analyser for gcc could potentially be helpful (as pylint was to Brett's update to the Python level guide), and Lennart also provides some more detailed practical suggestions in http://python3porting.com/cextensions.html

I'm sure there are other useful techniques that can be employed, but aren't necessarily well known outside the folks that have been busy implementing these migrations.

Barry, Petr, any of the other folks working on distro level C extension ports, perhaps one of you would be willing to consider an update to the C extension porting guide to be more in line with Brett's latest version of the Python level porting guide?

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