why did virtualenv not include all of the system paths?

I created a virtualenv, and while it has many system paths, it doesn't have others. Specifically, pyshared and di开发者_运维百科st-packages don't seem to be included. As a result, my system-wide MySQLdb and psycopg2 aren't available. Any ideas why?

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Seems to be related to Ubuntu's messing with python and virtualenv

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The only possible way that i'm aware of, is if you have created your virtualenv with the argument --no-site-packages:

from Here:

If you build with virtualenv --no-site-packages ENV it will not inherit any packages from /usr/lib/python2.5/site-packages (or wherever your global site-packages directory is). This can be used if you don't have control over site-packages and don't want to depend on the packages there, or you just want more isolation from the global system.

so Here is an example to understand more:

First i will create a virtualenv normally (without --no-site-package) and you will see that i can always access django that is installed in my system site-packages (or dist-packages):

$ virtualenv A
New python executable in A/bin/python
Installing setuptools............done
$ source A/bin/activate
(A)$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:57:41) 
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import django  
>>> django.__file__
'/usr/local/lib/python2.6/dist-packages/django/__init__.pyc'

But now i will create the virtual env using --no-site-package:

$ virtualenv B --no-site-package
New python executable in B/bin/python
Installing setuptools............done.
$ source B/bin/activate
(B)$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:57:41) 
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import django
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named django

now you see that virtaulenv was able to access django from system dist-packages (ubuntu) in my machine.

Hope this will help :)