I installed pyqt4 by using Homebrew. But when I import PyQt4 in python interpreter, It said that "No module named PyQt4". Can somebody help me with that?
It is likely that you are running the python executable from /usr/bin (Apple version) instead of /usr/loca/bin (Brew version)
You can either 
a) check your PATH variable
or 
b) run brew doctor
or 
c) run which python
to check if it is the case.
ImportError: No module named PyQt4