For programs that do not interact with the user in a continuous loop - programs that simply accept a set of arguments from the command line, return results, and do not keep the user within the program’s environment - all you need are sys.argv (the command-line arguments) and optparse (for parsing UNIX-style options and flags).
The curses module produces applications that interact via a plaintext terminal window, but are not limited to simple text input and output; they can paint the screen with options that are selected from using the cursor keys. However, programming a curses-based application is not as straightforward as using cmd.
Several packages in PyPI enable interactive command-line applications approximately similar in concept to cmd applications. None of them share cmd2’s close ties to cmd, but they may be worth investigating nonetheless.
I’ve found several alternatives to cmd in the Cheese Shop - CmdLoop, cly, CMdO, and pycopia. cly looks wonderful, but I haven’t been able to get it working under Windows, and that’s a show-stopper for many potential sqlpython users. In any case, none of the alternatives are based on cmd - they’re written from scratch, which means that a cmd-based app would need complete rewriting to use them. I like sticking close to the Standard Library whenever possible. cmd2 lets you do that.