Installation problem

Hi,

I dont have problem with installing PyQwt5 in global (non virtual) environment using command sudo apt-get install python-qwt5-qt4.
After installing, when I want to check the version, I get following:
~$ python -c 'import PyQt4.Qwt5; print PyQt4.Qwt5.QWT_VERSION_STR'
5.2.3

If i start virtual environment and execute exactly the same command, I get that PyQwt5 is successfully installed. However, when I want to see version of PyQwt this is what I get:
~$ python -c 'import PyQt4.Qwt5; print PyQt4.Qwt5.QWT_VERSION_STR'
Traceback (most recent call last):
File "<string>", line 1, in <module>
ImportError: No module named Qwt5

What is the problem?

Many thans,
Aratar