Why do distribute and pip install to my virtualenv's ./local/bin?

Question

I create and activate a virtualenv (venv) using Python 3.3's built-in way of doing it:

$ python3.3 -m venv env $ source env/bin/activate 

At this point python is the python in my virtualenv, which I expect:

(env) $ which python /my_home_directory/env/bin/python 

Now I want to install distribute and pip, so I download the setup scripts and run them:

(env)$ wget http://python-distribute.org/distribute_setup.py (env)$ wget https://raw.github.com/pypa/pip/master/contrib/get-pip.py (env)$ python distribute_setup.py (env)$ python get-pip.py 

These commands complete successfully. At this point I inspect my venv to find another directory called "local" which wasn't there before. env/local/bin contains my easy_install and pip executables, and they're still aliased to my system's existing easy_install and pip:

(env)$ ls env bin  include  lib  local  pyvenv.cfg (env)$ ls env/bin activate  pydoc  python  python3  python3.3 (env)$ ls env/local/bin easy_install  easy_install-3.3  pip  pip-3.3 (env)$ which easy_install /usr/bin/easy_install (env)$ which pip /usr/bin/pip 

I believe this is a departure from Python 2.x's behavior. At this point I expect easy_install and pip to be using the virtualenv's copies, and using them to install eggs will put them in the virtualenv.

Going a bit further, I crack open env/bin/activate to find that env/bin is prepended to the system path, but env/local/bin is not. That explains the behavior I'm seeing. I can work around this problem by editing env/bin/activate to add the env/local/bin directory to the path, something like:

_OLD_VIRTUAL_PATH="$PATH" PATH="$VIRTUAL_ENV/bin:$PATH" PATH="$VIRTUAL_ENV/local/bin:$PATH"  # my new line export PATH 

So, what's going on here? Is this a bug, or am I missing something?

I'm on Ubuntu 12.10 in case that makes a difference.

Answer 1

I have a feeling there's a bug in Ubuntu's python packages or distribute somewhere… but I haven't tracked it down (and I'm not sure I care to).

For whatever reason, the VIRTUAL_ENV environment variable needs to be set the root of the virtualenv for distribute and pip to install properly.

This gist, adopted from Vinay Sajip's code sample in the Python 3 docs, sets said variable; both distribute and pip will install properly when using it.