I am using Python2.6. I am trying to list the disk drives that a system may have.
On Windows, it may be something like C:/, D:/, E:/
There isn't really a unified naming scheme for Linux devices that guarantees you a formatable block device. There are conventions, but they can vary widely and I can call my thumb-drive /Thomas/O if I want and there is no cross-platform way in Python to know:
I'm pretty sure that neither is there a cross-platform Python module which will allow you to determine that H:/ is formattable on a Windows system but that Z:/ is not.
Each system will require its own specific checks and validations which you could best learn from studying open-source disk manipulation software.