site-packages dir empty but OpenCV works...what the?

Question

I used the following to install opencv

sudo apt-get install libopencv-dev python-opencv

I can "import cv2" fine, read images, manipulate them to my hearts content...everything works great! However, my usr/local/lib/python2.7/site-packages folder is empty!! How can that be?

I'm trying to use virtualenv but according to this I need to install numpy and opencv globally (which I have done successfully) and then copy cv* from the global site-packages dir to the virtual environment site-packages dir. But, my global site-packages dir is empty!

I do see some cv* stuff on my pi:

usr/lib/pyshared/python2.7/cv2.so
usr/lib/pymodules/python2.7/cv2.so
usr/lib/pymodules/python2.7/cv.pyc
usr/lib/pymodules/python2.7/cv.py

I copied the items from usr/lib/pymodules/python2.7/cv* to my virtualenv site-packages dir but still no love...

>>> import cv2
ImportError: numpy.core.multiarray failed to import
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: numpy.core.multiarray failed to import

Answer 1

I got this to work and I will spell out what I did but not sure exactly WHY it worked so feel free to educate me with another answer or comments.

After copying the cv* to my virtualenv dir I ran this (even though I had run it just prior to sudo pip install virtualenv)...

sudo apt-get update
sudo apt-get install python-dev

I then activated my virtualenv and ran this...

pip install numpy

which took a LONG time to do its thing! Without the apt-gets above this would fail very quickly because of not finding some .h files. But now I can import cv2 and numpy into my virtualenv!!