I am developing a paid application in python. I do not want the users to see the source code or decompile it. How can I accomplish this task to hiding the source code from the user but running the code perfectly with the same performance.
To a determined user, you can't.
From a practical standpoint, you can do some tricks, such as wrapping it into a binary executable or using obfuscation.
See here for full details: http://stackoverflow.com/questions/261638/how-do-i-protect-python-code
There's no use in doing that.
If your application is not incredibly small and simple, then even if the client (or other programmers they hired) were to work on that code, they'd still need a lot of your help with it.
If it is incredibly small and simple, don't even bother with it. The client could just get someone to rewrite it from scratch anyway.