What does it take to implement a chat system in Python (Not asking for code just advice before I start my little project)

[Aseem Bansal]

@Andrew Berg
@Chris Angelico

Is there a way to have both Python 2 and 3 installed on my computer till I can update the little codebase that I have built? Can I make different commands for invoking python 2 and Python 3? I am using Windows 7 and use Windows Powershell as an alternative to the linux terminal. Any suggestions about how to do that instead of breaking all my code at once?