Generating unique random numbers but in order - python

I have a question. In python, we can use the random module to generate random numbers. I need numbers from 0 to the system's maximum size (can be determined by sys.maxsize). How do I get all the numbers in order (like 0,1,2,3,4.......) and how can I generate unique ones (do not repeat again)? If possible, can someone attach the code for doing this?