It is not either&#x2F;or.<p>I think there is simply a miscommunication happening here, where folks unfamiliar with iPython are assuming it is a simple REPL (like the Perl debugger in REPL mode. I&#x27;m not talking about a dumb thing that executes one line of code and returns. iPython (and, again, I imagine the better Lisp and SmallTalk REPLs) is a full shell with your programming environment available, including the ability to use the debugger interactively, explore your data structures, etc. But, you can also create new functions, modify existing ones, and it has command history, etc. All the stuff you&#x27;d expect of a good shell, but in Python and with a complete picture of your program&#x27;s execution environment.<p>I&#x27;ve simply never felt like I was able to get inside of a program like when working with iPython, and I&#x27;m not at all a good Python programmer.