Even though the package is successfully installed, it is possible that I get this ImportError: No module named <package>. This is because I have several different Python interpreters and the specific Python interpreter that I am using does not have the path that the package. So, print out this in the very first line of the code:
import sys; print(sys.path)
And see if any of the paths has the specific package I am looking for. If not, 1) add the path that the package is installed or 2) install the package in the interpreter that I want to use.