[Python-Dev] .pth files are evil

[P.J. Eby]

At 04:42 PM 5/9/2009 +0200, Martin v. Löwis wrote:
> >> If you always use --single-version-externally-managed with easy_install,
> >> it will stop editing .pth files on installation.
> >
> > It's --multi-version (-m) that does that.
> > --single-version-externally-managed is a "setup.py install" option.
> >
> > Both have the effect of not editing .pth files, but they do so in
> > different ways.  The "setup.py install" option causes it to install in a
> > distutils-compatible layout, whereas --multi-version simply drops .egg
> > files or directories in the target location and leaves it to the user
> > (or the generated script wrappers) to add them to sys.path.
>
>Ah, ok. Is there also an easy_install invocation that unpacks the zip
>file into some location of sys.path (which then wouldn't require
>editing sys.path)?

Not as yet.  I'm sort of waiting to see what comes out of PEP 376 
discussions re: an installation manifest...  but then, if I actually 
had time to work on it right now, I'd probably just implement something.

Currently, you can use pip to do that, though, as long as the 
packages you want are in source form.  pip doesn't unzip eggs as yet.

It would be really straightforward, though, for someone to implement 
an easy_install variant that does this.  Just invoke "easy_install 
-Zmaxd /some/tmpdir packagelist" to get a full set of unpacked .egg 
directories in /some/tmpdir, and then move the contents of the 
resulting .egg subdirs to the target location, renaming EGG-INFO 
subdirs to projectname-version.egg-info subdirs.

(Of course, this ignores the issue of uninstalling previous versions, 
or overwriting of conflicting files in the target -- does pip handle these?)