Re: [gentoo-dev] [RFC] A news item covering PYTHON_TARGETS

[Michał Górny]

On Mon, 29 Oct 2012 15:45:01 +0100
Michał Górny <mgorny@g.o> wrote:

> Since some ebuilds are using that variable already and we still didn't
> inform most of our users if and how they should set it, I'd like to
> commit the following news item:

Thank you for all your suggestions, and especially Duncan for wording
the hardest paragraph for me ;). I've also tried to make the remaining
ones clearer.

Title: PYTHON_TARGETS deployment
Author: Michał Górny <mgorny@g.o>
Content-Type: text/plain
Posted: 2012-10-29
Revision: 1
News-Item-Format: 1.0

Recently, a few new Python eclasses were deployed. As ebuilds migrate,
the way they support multiple Python implementations will change.
The previous method built Python modules for all currently installed
Python implementations. The new one uses the PYTHON_TARGETS USE flags to
explicitly name the implementations the modules shall be built for.

If you are running a modern system with Python 2.7 & 3.2 being the only
installed Python implementations, then you don't have to do anything.
The defaults will simply fit you, and let you keep your system
up-to-date when new Python versions are deployed.

However, if you'd like to use another set of Python implementations, you
will want to set PYTHON_TARGETS in your make.conf file appropriately.
This variable names the enabled implementations in the standard way
common to all USE_EXPAND variables.

For example, a setup enabling all major Python implementations would
look like:

	PYTHON_TARGETS="python2_7 python3_2 pypy1_9 jython2_5"

The variable should list all Python implementations which are going to
be used on the system; missing a particular value there will result
in missing Python modules.

A complete list of all possible values can be obtained using a command
equivalent to the following:

	emerge -1pv dev-python/python-exec

-- 
Best regards,
Michał Górny