python 2 and 3 modules

[Marcus von Appen]

Baptiste Daroussin <bapt at freebsd.org>:

> On Mon, Jul 29, 2013 at 12:26:24PM +0200, Marcus von Appen wrote:
>> David Demelier <demelier.david at gmail.com>:
>>
>> > 2013/7/29 Marcus von Appen <mva at freebsd.org>:
>> >> David Demelier <demelier.david at gmail.com>:
>> >>
>> >>
>> >>> 2013/7/28 Daniel Braniss <danny at cs.huji.ac.il>:
>> >>>>
>> >>>> Hi,
>> >>>> I need to be able to have both (2.7 and 3.2) modules.
>> >>>> setting PYTHON_VERSION=3.2 in /etc/make.conf compiles properly,
>> >>>> but make install, insists that that the 2.7 version is installed!
>> >>>> after deinstalling, it will install the 3.2 version in the correct
>> >>>> directory:
>> >>>>         /usr/local/lib/python3.2/site-path
>> >>>> but now I lost the 2.7 version.
>> >>>>
>> >>>> the same happens if I try to install the 2.7 version, it will complain
>> >>>> that the 3,2 version is installed.
>> >>>>
>> >>>> BTW, the comments in ports/Mk/bsd.python.mk are very confusing and
>> >>>> some are wrong:
>> >>>> # PYTHON_VERSION        - Version of the python binary in your ${PATH},
>> >>>> in the
>> >>>> #                                         format "python2.0".  
>> Set this in
>> >>>> your
>> >>>> makefile in case you
>> >>>> #                                         want to build extensions with
>> >>>> an
>> >>>> older binary.
>> >>>> #                                         default: depends on  
>> the version
>> >>>> of
>> >>>> your python binary
>> >>>>
>> >>>> setting it to "python3.2" produces errors in the make, while 3.2 is ok
>> >>>>
>> >>>> is there any fix?
>> >>>>
>> >>>> thanks,
>> >>>>         danny
>> >>>>
>> >>>
>> >>> For the moment its pretty difficult to install python 2.7 and 3.3 at
>> >>> the same time. However, if you plan to install python 3.3, you need to
>> >>> set PYTHON_DEFAULT_VERSION to "python3.3" and not PYTHON_VERSION.
>> >>
>> >>
>> >> No, it is not.
>> >>
>> >> cd /usr/ports/lang/python27 && make install clean
>> >> cd /usr/ports/lang/python32 && make install clean
>> >> cd /usr/ports/lang/python33 && make install clean
>> >>
>> >> works like a charm. If you however want to use Python modules, it might
>> >> become
>> >> more difficult. It was discussed some time ago on the  
>> freebsd-python mailing
>> >> list
>> >> without an applicable result.
>> >>
>> >> If you need to have the same Python module for different  
>> versions around, I
>> >> would
>> >> recommend to use virtualenv in favour of the ports infrastructure, since
>> >>
>> >> make -DPYTHON_DEFAULT_VERSION=xxx <python-module>    - or -
>> >> make -DPYTHON_VERSION=xxx <python-module>     - or -
>> >> make -DPYTHON3_DEFAULT_VERSION=xxx <python-module>
>> >>
>> >> might mess up previous installations for a different python version.
>> >>
>> >> Cheers
>> >> Marcus
>> >>
>> >
>> > Of course from ports it will work. I've told about binary packages.
>> >
>> > When you bulk build a package for python 2.7 and python 3.3 the
>> > /usr/local/bin/python will be included in both versions. Because bulk
>> > building python 3 modules will requires to set PYTHON_DEFAULT_VERSION
>> > and PYTHON3_DEFAULT_VERSION to the python 3.3 interpreter.
>> >
>> > Then the poudriere bulk will generate python 2.7 and python 3.3
>> > pkg-plist including for both /usr/local/bin/python and all of the
>> > non-versioned files I've already told above.
>> >
>> > You may now think "who cares? it build from ports". I would say no,
>> > binary packages will be used more and more in the future.
>>
>> I would not, either. This however is a problem with the package builder
>> and ports infrastructure, which would need some install hooks to allow
>> a check at installation time.
>>
> That is totally wrong, that is a python bug (python is not the only  
> one in that
> case).

It is not wrong. You just misunderstood me.

> The ports have only be design for source installation, problem is  
> when you are
> buidling packages properly each packages are being done in a cleanroom aka a
> jail without anything installed in it that makes python 3.3 port think it is
> becoming the default because no other python are installed at that time.
>
> This result in all python port defining bin/python, and thus they  
> _do_ conflict
> with each other. While this was/is silent with pkg_install, pkgng  
> yell about it.

On the port level, yes, with the IF_DEFAULT conditional.
We have lang/python, which acts as wrapper; what conditional in
the package builder triggers either port of lang/pythonXX to install itself
as default (except for the current default version defined in bsd.python.mk,
which uses _PYTHON_PORTBRANCH for that)? If I closely follow the port logic,
only lang/python27 should be picked as default, if no specific flags are
provided. Or I'm missing something obvious in the bsd.python.mk logic.

>
> A fun thing you can do with pkg_install (in binary mode only no  
> compilation from
> sources and with packages built in a cleanroom)
> # pkg_add -r python27
> default is now python27
> # pkg_add -r python33
> default is now python33
> # pkg_delete python27
> hey I have no default python anymore.

If that is really the case (I can only confirm that for lang/python27),
let's get it fixed on the bsd.python.mk and lang/pythonXX level and let
lang/python do the magic, which it is supposed to do.

> Java is solving the problem by using a javawrapper. There is 3  
> possible way to
> solve the situation with python, move the symlink dancing into a post install
> script. Have a javawrapper like thing.

The post-install script is what I was talking about above. So we both  
mean the same.
Anyways, we have lang/python, which would be the best place in my opinion.

Cheers
Marcus