How do you correct Module already loaded UserWarnings in Python?

Question

Getting the following kinds of warnings when running most python scripts in the command line:

/Library/Python/2.6/site-packages/virtualenvwrapper/hook_loader.py:16: UserWarning: Module 

pkg_resources was already imported from /System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.pyc, but /Library/Python/2.6/site-packages is being added to sys.path
  import pkg_resources

/Library/Python/2.6/site-packages/virtualenvwrapper/hook_loader.py:16: UserWarning: Module site was already imported from /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site.pyc, but /Library/Python/2.6/site-packages is being added to sys.path
  import pkg_resources

I think it has to do with a combination of using distribute and virtualenv, but wanted to check if anyone else has run in to this or would know how to go about fixing it.

Answer 1

Perhaps use the virtualenv option --no-site-packages so you won't see any system site-packages within your virtual environment. Having items installed both in your virtualenv and on the system root may be the cause of this issue.

Using --no-site-packages when creating your virtualenv prevents any conflict between system packages. I almost always use that option when creating a new virtualenv to prevent any conflicts. Though I may have several copies of libraries, at least they don't mess with each other.

Answer 2

The python equivalent of putting a bit of electrical tape over the check engine light would be to use the -W command line flag or by adding a warning filter.

Answer 3

In my case reinstalling of anything did not help. There were some orphaned .pyc files (specifically pkg_resources.pyc) left in /System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python

sudo find . -type f -name "*.pyc" -delete

made it work. This link helped me to track down the problem.