[Python-Dev] PEP 394 request for pronouncement (python2 symlink in *nix systems) (original) (raw)

Ned Deily nad at acm.org
Sun Feb 19 10:29:50 CET 2012

In article <4F3CD403.7070102 at v.loewis.de>, "Martin v. Lowis" <martin at v.loewis.de> wrote:

> There are two issues that I know of for OS X. One is just getting a > python2 symlink into the bin directory of a framework build. That's > easy.

Where exactly in the Makefile is that reflected? ISTM that the current patch already covers that, since the framwork* targets are not concerned with the bin directory.

When a framework build is enabled in configure, several additional targets from Mac/Makefile are called from the main Makefile. The creating of the links in the framework bin directory and in $prefix/bin (/usr/local/bin) are handled there. (See the checked in patch for 2.7 for gory details: http://hg.python.org/cpython/rev/499796937b7a)

> The other is managing symlinks (python, python2, and python3) > across framework bin directories; currently there's no infrastructure > for that. That part will probably have to wait until PyCon.

What is the "framework bin directory"? The links are proposed for /usr/local/bin resp. /usr/bin. The proposed patch already manages these links across releases (the most recent install wins).

The framework bin directory is a bin directory within a framework. The default location for 2.7 is:

/Library/Frameworks/Python.framework/Versions/2.7/bin

This is where the python executable, aux programs like idle, 2to3, pydoc, python-config, as well as all Distutils-installed scripts go.
Mac/Makefile and the Mac installer each optionally create symlinks from /usr/local/bin (default) to the items in the framework bin directory at build or install time for the standard items but not for subsequent Distutils-installed scripts. Normally, the /usr/local/bin links are not needed with framework builds as the framework bin directory is added to the user's $PATH during installation.

If you are concerned about multiple feature releases: this is not an issue, since the links are just proposed for Python 2.7 (distributions may also add them for 2.6 and earlier, but we are not going to make a release in that direction).

It is more of an issue for multiple Python 3 versions. But the whole mechanism of managing multiple framework versions (2 and/or 3) is messy right now. But that's a separate topic that I plan to address later.
As for now, I believe all that is needed for PEP 394 is now checked-in.

-- Ned Deily, nad at acm.org

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