title: How to share libraries between virtual environments and/or python installation
body: <p>There is 2 situation:</p>
  
  <p>1) I was trying to install pygtk in my virtual environment. py2cairo caused errors so i couldn't install. Then i linked pygtk and py2cairo in my python installation to my virtual enviroment as offered in here >> <a href="https://stackoverflow.com/questions/12830662/python-package-installed-globally-but-not-in-a-virtualenv-pygtk">Python package installed globally, but not in a virtualenv (PyGTK)</a></p>
  
  <p>2) I have many virtual environments for my django applications in my server. All have common django package in same version in nearly  all my virtual enviroments. And so in every virtual environment there is a django copy again and again.</p>
  
  <p>For these 2 situation linking could work as charm but !</p>
  
  <p><strong>Question</strong>: i still cant find any solution how to make pip to see these packages.</p>
  
  <p><strong>PS</strong>: Or any better approach for this problem?</p>