title: How to override certain library versions in Python's site-packages folder
body: <p>Let's say I have a lib called libfoo installed inside Python's site-packages folder. Thus libfoo has become a system wide lib. Now I have a python script that needs to use a newer version of libfoo but don't want to install it system wide just in case other script is using the older version, is there a way to tell the script "Please use the libfoo version in another location instead of system wide one"?</p>
  
  <p>Please don't tell me "You should use virtulenv". I know virtualenv. I ask this question just to understand the priority of python paths.</p>