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   "cell_type": "markdown",
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   "source": [
    "# How to add a custom system prompt to the prebuilt ReAct agent\n",
    "\n",
    "This tutorial will show how to add a custom system prompt to the prebuilt ReAct agent. Please see [this tutorial](./create-react-agent.ipynb) for how to get started with the prebuilt ReAct agent\n",
    "\n",
    "You can add a custom system prompt by passing a string to the `messages_modifier` param."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "7be3889f-3c17-4fa1-bd2b-84114a2c7247",
   "metadata": {},
   "source": [
    "## Setup"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "a213e11a-5c62-4ddb-a707-490d91add383",
   "metadata": {},
   "outputs": [],
   "source": [
    "%%capture --no-stderr\n",
    "%pip install -U langgraph langchain-openai"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "23a1885c-04ab-4750-aefa-105891fddf3e",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "OPENAI_API_KEY:  ········\n"
     ]
    }
   ],
   "source": [
    "import getpass\n",
    "import os\n",
    "\n",
    "\n",
    "def _set_env(var: str):\n",
    "    if not os.environ.get(var):\n",
    "        os.environ[var] = getpass.getpass(f\"{var}: \")\n",
    "\n",
    "\n",
    "_set_env(\"OPENAI_API_KEY\")\n",
    "\n",
    "# Recommended\n",
    "_set_env(\"LANGCHAIN_API_KEY\")\n",
    "os.environ[\"LANGCHAIN_TRACING_V2\"] = \"true\"\n",
    "os.environ[\"LANGCHAIN_PROJECT\"] = \"Create ReAct Agent Tutorial\""
   ]
  },
  {
   "cell_type": "markdown",
   "id": "03c0f089-070c-4cd4-87e0-6c51f2477b82",
   "metadata": {},
   "source": [
    "## Code"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "7a154152-973e-4b5d-aa13-48c617744a4c",
   "metadata": {},
   "outputs": [],
   "source": [
    "# First we initialize the model we want to use.\n",
    "from langchain_openai import ChatOpenAI\n",
    "\n",
    "model = ChatOpenAI(model=\"gpt-4o\", temperature=0)\n",
    "\n",
    "\n",
    "# For this tutorial we will use custom tool that returns pre-defined values for weather in two cities (NYC & SF)\n",
    "\n",
    "from typing import Literal\n",
    "\n",
    "from langchain_core.tools import tool\n",
    "\n",
    "\n",
    "@tool\n",
    "def get_weather(city: Literal[\"nyc\", \"sf\"]):\n",
    "    \"\"\"Use this to get weather information.\"\"\"\n",
    "    if city == \"nyc\":\n",
    "        return \"It might be cloudy in nyc\"\n",
    "    elif city == \"sf\":\n",
    "        return \"It's always sunny in sf\"\n",
    "    else:\n",
    "        raise AssertionError(\"Unknown city\")\n",
    "\n",
    "\n",
    "tools = [get_weather]\n",
    "\n",
    "# We can add our system prompt here\n",
    "\n",
    "prompt = \"Respond in Italian\"\n",
    "\n",
    "# Define the graph\n",
    "\n",
    "from langgraph.prebuilt import create_react_agent\n",
    "\n",
    "graph = create_react_agent(model, tools=tools, messages_modifier=prompt)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "00407425-506d-4ffd-9c86-987921d8c844",
   "metadata": {},
   "source": [
    "## Usage\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "16636975-5f2d-4dc7-ab8e-d0bea0830a28",
   "metadata": {},
   "outputs": [],
   "source": [
    "def print_stream(stream):\n",
    "    for s in stream:\n",
    "        message = s[\"messages\"][-1]\n",
    "        if isinstance(message, tuple):\n",
    "            print(message)\n",
    "        else:\n",
    "            message.pretty_print()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "9ffff6c3-a4f5-47c9-b51d-97caaee85cd6",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "================================\u001b[1m Human Message \u001b[0m=================================\n",
      "\n",
      "What's the weather in NYC?\n",
      "==================================\u001b[1m Ai Message \u001b[0m==================================\n",
      "Tool Calls:\n",
      "  get_weather (call_b02uzBRrIm2uciJa8zDXCDxT)\n",
      " Call ID: call_b02uzBRrIm2uciJa8zDXCDxT\n",
      "  Args:\n",
      "    city: nyc\n",
      "=================================\u001b[1m Tool Message \u001b[0m=================================\n",
      "Name: get_weather\n",
      "\n",
      "It might be cloudy in nyc\n",
      "==================================\u001b[1m Ai Message \u001b[0m==================================\n",
      "\n",
      "A New York potrebbe essere nuvoloso.\n"
     ]
    }
   ],
   "source": [
    "inputs = {\"messages\": [(\"user\", \"What's the weather in NYC?\")]}\n",
    "\n",
    "print_stream(graph.stream(inputs, stream_mode=\"values\"))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "3decf001-7228-4ed5-8779-2b9ed98a74ea",
   "metadata": {},
   "outputs": [],
   "source": []
  }
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