python - Virtualenv on Ubuntu with no site-packages

Question

I've been using virtualenv lately while developing in python. I like the idea of a segregated development environment using the --no-site-packages option, but doing this while developing a PyGTK app can be a bit tricky. The PyGTK modules are installed on Ubuntu by default, and I would like to make a virtualenv (with --no-site-packages) aware of specific modules that are located elsewhere on the system.

What's the best way to do this? Or should I just suck it up and drop the --no-site-packages option?

Answer 1

$ virtualenv --no-site-packages --python=/usr/bin/python2.6 myvirtualenv
$ cd myvirtualenv
$ source bin/activate
$ cd lib/python2.6/
$ ln -s /usr/lib/pymodules/python2.6/gtk-2.0/ 
$ ln -s /usr/lib/pymodules/python2.6/pygtk.pth 
$ ln -s /usr/lib/pymodules/python2.6/pygtk.py 
$ ln -s /usr/lib/pymodules/python2.6/cairo/
$ python
>>> import pygtk
>>> import gtk

Answer 2

One way is to add the paths to your code using sys.path.

import sys

sys.path.append(somepath)

Another way is to use site, which processes .pth files in addition to adding to sys.path.

import site

site.addsitedir(sitedir, known_paths=None)

https://docs.python.org/library/site.html

But you probably don't want to add this to all your related code.

I've seen mention of sitecustomize.py being used to perform something like this, but after some testing I couldn't get it to work as might be expected.

Here it mentions that auto-import of sitecustomize.py ended in 2.5, if your not on 2.5 try it out. (just add one of the path add methods above to the file and drop it in the directory your program is run) A work around method is mentioned in the post for users of 2.5 and up.

http://code.activestate.com/recipes/552729/

Answer 3

I find in this situation, symlinks, or even copying specific files (packages, modules, extensions) works really well.

It allows the program to emulate being run in the target environment, rather than changing the application to suit the development environment.

Same deal for something like AppEngine.

Answer 4

Check out the postmkvirtualenv hook script here:

https://stackoverflow.com/a/9716100/60247

In that case, he's using it to import PyQt and SIP after a new Virtualenv is created, but you can add the packages that you need to LIBS.

And vote that script up because it's fantastic :)

Answer 5

If you want to include the links to the relevant system's python gtk-2.0 in the virtualenv, you can just use pip to install ruamel.venvgtk:

pip install ruamel.venvgtk You don't have import anything, the links are setup during installation.

This is especially handy if you are using tox, in that case you only need to include the dependency (for tox):

deps:
    pytest
    ruamel.venvgtk

and a newly setup python2.7 environment will have the relevant links included before the tests are run.

More detailed information on how the links are setup can be found in this answer