Modify a python package installed as a single EGG file

Sometimes, you want to modify a python package installed in your python library. How about if you see the package youjust installed is a single .egg file? You could still open it with your favorite decompress program, such as 7zip, since we know .egg file is just a ZIP file. After decompress you get folders which contain regular.py and .pyc file for you to work on. Then you can put the decompressed folder into your site-package directory keeping the same name (use original .egg name as directory name).