Agents in 60 lines of python : Part 3

The Agent Loop The entire AI agent stack in 60 lines of Python. You've seen Claude search files, read them, then search again. ChatGPT with Code Interpreter writes code, runs it, sees an error, fixes it, runs again. That back-and-forth isn't magic. It's a loop. Lesson 2's agent made one tool call and stopped. That's fine for "what's 2 + 2?" but useless for anything real. Multi-step tasks — analyzing a codebase, debugging a function, researching a topic — need the agent to keep going until the job is done. The agent loop is what makes that possible. And it's shockingly simple. The concept Real agents loop: call a tool, see the result, decide what's next, repeat until done. The LLM decides when to stop. The flow is: Build messages — system prompt + user task Ask LLM — send everything so far tool_calls? — the LLM either returns an answer (done) or asks for tools Execute tool — run it, append the result Back to Ask LLM — with the growing messages array That loop-back arrow from "Execute to