Why does pip freeze report some packages in a fresh virtualenv created with --no-site-packages?

Question

When I create a fresh virtualenv, pip freeze shows that I have a couple of packages installed even though I've not installed anything into the environment. I was expecting pip freeze to return empty output until after my first pip install into the environment. wsgiref is part of the standard library isn't it, so why does it show up at all?

 day@garage:~$ mkdir testing day@garage:~$ cd testing day@garage:~/testing$ virtualenv --no-site-packages . New python executable in ./bin/python Installing distribute.......................................................... ............................................................................... .........................................done. day@garage:~/testing$ . bin/activate (testing)day@garage:~/testing$ pip freeze distribute==0.6.10 wsgiref==0.1.2 

Some extra info:

 (testing)day@garage:~/testing$ pip --version pip 0.7.2 from /home/day/testing/lib/python2.7/site-packages/pip-0.7.2-py2.7.eg g (python 2.7) (testing)day@garage:~/testing$ deactivate day@garage:~/testing$ virtualenv --version 1.4.9 day@garage:~/testing$ which virtualenv /usr/bin/virtualenv day@garage:~/testing$ dpkg -S /usr/bin/virtualenv python-virtualenv: /usr/bin/virtualenv day@garage:~/testing$ cat /etc/lsb-release  DISTRIB_ID=Ubuntu DISTRIB_RELEASE=11.04 DISTRIB_CODENAME=natty DISTRIB_DESCRIPTION="Ubuntu 11.04" 

Answer 1

Everytime you create a virtualenv with --no-site-packages it installs setuptools or distribute. And the reason wsgiref appears is because python 2.5+ standard library provides egg info to wsgiref lib (and pip does not know if it stdlib or 3rd party package).

It seems to be solved on Python3.3+: http://bugs.python.org/issue12218