From a computer-centered perspective, interactive computing has been formalized by modelling these systems as persistent Turing machines coupled to an environment (the human user) \cite{2006}. More colloquially, the simplest expression of an interactive computation is the REPL, or read-eval-print loop. In a REPL, the program repeatedly reads lines of code, evaluates that code, and then prints the result. Simple terminal-based interactive shells like IPython, as well as the Jupyter Notebook, follow this pattern with minor variations. But the computer-centered perspective doesn’t answer the question posed above: what is the value of a REPL from the human perspective?