IPython has to my knowledge always used those kind of labels for inputs and outputs. It just follows from the CLI convention. I looked up how it was in version

IPython has to my knowledge always used those kind of labels for inputs and outputs. It just follows from the CLI convention. I looked up how it was in version 0.0.1 from 12 years ago and it turns out the original CLI format was made to look like Mathematica [1]: "Interactive execution with automatic history, tries to mimic Mathematica's prompt system". [1] https://gist.github.com/fperez/1579699 https://gist.github.com/fperez/1579699