[Distutils] easy_install and Unix python with sys.prefix different from sys.exec_prefix

[Phillip J. Eby]

At 03:22 PM 11/1/2006 +0100, Berthold Höllmann wrote:
>Is there a way to fix these problems?

Set your desired installation paths in one of your configuration files; see 
the easy_install docs for details.

Note, however, that easy_install doesn't have to install to different 
locations for platform-specific code, because it installs files or 
directories that include platform information in the filename!  So, there's 
nothing wrong with having a single shared installation directory, as long 
as you use --multi-version to allow different platform versions to 
co-exist, without having a default version.

The downside to this approach is that if you start the Python interpreter 
manually instead of via a setuptools-based #! script, then the packages 
will not be importable without first calling require().  Of course, you can 
remedy that with a sitecustomize.py containing e.g.:

     from pkg_resources import require
     require('somepkg', 'otherpkg', ...)

Which would do basically the same thing as having an easy-install.pth, 
except that it's not platform-specific.

The other alternative to this is that you simply use your NFS directory as 
a cache for easy_install.  The way this would work is that you install 
things with two easy_install steps for each platform:

     easy_install -zmaxd /path/to/shared/directory SomePackageName
     easy_install -f /path/to/shared/directory SomePackageName

The first line will download/build/etc. and just dump the eggs to the 
shared directory, without creating a .pth or scripts, etc.  Then, the 
second line will install the .pth and scripts, assuming you've configured 
easy_install's library and script installation directories to be your 
platform-specific directories.  (Note: you would have to have a 
platform-specific scripts directory, because the #! line is going to point 
to the platform-specific Python.)

This approach allows you to avoid re-installing platform-generic libraries, 
because they will be found in the cache directory without downloading.