[Python-Dev] versioned .so files for Python 3.2

[Brett Cannon]

On Fri, Jun 25, 2010 at 01:53, Scott Dial
<scott+python-dev at scottdial.com> wrote:
> On 6/24/2010 8:23 PM, James Y Knight wrote:
>> On Jun 24, 2010, at 5:53 PM, Scott Dial wrote:
>>> If the package has .so files that aren't compatible with other version
>>> of python, then what is the motivation for placing that in a shared
>>> location (since it can't actually be shared)
>>
>> Because python looks for .so files in the same place it looks for the
>> .py files of the same package.
>
> My suggestion was that a package that contains .so files should not be
> shared (e.g., the entire lxml package should be placed in a
> version-specific path). The motivation for this PEP was to simplify the
> installation python packages for distros; it was not to reduce the
> number of .py files on the disk.

I assume you are talking about PEP 3147. You're right that the PEP was
for pyc files and that's it. No one is talking about rewriting the
PEP. The motivation Barry is using is an overarching one of distros
wanting to use a single directory install location for all installed
Python versions. That led to PEP 3147 and now this work.

>
> Placing .so files together does not simplify that install process in any
> way. You will still have to handle such packages in a special way. You
> must still compile the package multiple times for each relevant version
> of python (with special tagging that I imagine distutils can take care
> of) and, worse yet, you have created a more trick install than merely
> having multiple search paths (e.g., installing/uninstalling lxml for
> *one* version of python is actually more difficult in this scheme).

This is meant to be used by distros in a programmatic fashion, so my
response is "so what?" Their package management system is going to
maintain the directory, not a person. You and I are not going to be
using this for anything. This is purely meant for Linux OS vendors
(maybe OS X) to manage their installs through their package software.
I honestly do not expect human beings to be mucking around with these
installs (and I suspect Barry doesn't either).

>
> Either the motivation for this PEP is inaccurate or I am failing to
> understand how this is *simpler*. In the case of pure-python, this PEP
> is clearly a win, but I have not seen an argument that it is a win for
> .so files. Moreover, the PEP itself is titled "PYC Repository
> Directories" (not "shared site-packages") and makes no mention of .so
> files at all.

You're conflating what is being discussed with PEP 3147. That PEP is
independent of this. PEP 3147 just empowered this work to be relevant.

-Brett

>
> --
> Scott Dial
> scott at scottdial.com
> scodial at cs.indiana.edu
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