Definition
Plain language
A way of interacting with a programming language by typing commands and seeing results immediately.
As stated in the literature
Read-Eval-Print Loop — an interactive prompt that evaluates expressions one at a time and prints their results.
Why it matters: REPLs let an agent or human probe a system interactively, which makes them indispensable for debugging and exploration.
For example, a Python REPL lets you type `2 + 2`, see `4`, and then type `print('hi')` — each line evaluated the moment you hit enter.
Heard on the show
“The agent is what's called a Python REPL agent — it interleaves chain of thought with executing actual Python code.”Episode 028 — Teaching a Model to Hire Copies of Itself: Recursive Agent Optimization