Build an AI agent from scratch in under 50 lines of pure Python: ReAct loop tutorial
adnan_hashmi · x · 2026-10-26
aiagent.org published a 25-minute, zero-framework tutorial (Python 3.10+) on building AI agents from scratch to production:
- Mental model: standard LLM chat is stateless one-shot Q&A; an agent = LLM brain + tools + memory + a decision loop that calls tools, observes outcomes, and self-corrects.
- Implementation: a working agent in under 50 lines of pure Python — essentially a while-loop around the ReAct reasoning cycle, no LangChain/CrewAI needed. The accompanying flowchart shows the full loop: build system prompt & tool schemas → call LLM → extract tool calls → execute local tools/APIs → append results to history → stream final answer, with a max-iteration safety abort.
- Beyond basics: adding memory and moving to production multi-agent systems; a 10-module bootcamp series covers LangGraph, CrewAI, AutoGen, and MCP with 15+ runnable repos.
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