langchain/docs/examples/prompts/custom_prompt_template.ipynb

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    "# Custom Prompt Template\n",
    "\n",
    "This notebook goes over how to create a custom prompt template, in case you want to create your own methodology for creating prompts.\n",
    "\n",
    "The only two requirements for all prompt templates are:\n",
    "\n",
    "1. They have a `input_variables` attribute that exposes what input variables this prompt template expects.\n",
    "2. They expose a `format` method which takes in keyword arguments corresponding to the expected `input_variables` and returns the formatted prompt.\n",
    "\n",
    "Let's imagine that we want to create a prompt template that takes in input variables and formats them into the template AFTER capitalizing them. "
   ]
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  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "26f796e5",
   "metadata": {},
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   "source": [
    "from langchain.prompts import BasePromptTemplate\n",
    "from pydantic import BaseModel"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "27919e96",
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   "source": [
    "class CustomPromptTemplate(BasePromptTemplate, BaseModel):\n",
    "    template: str\n",
    "        \n",
    "    def format(self, **kwargs) -> str:\n",
    "        capitalized_kwargs = {k: v.upper() for k, v in kwargs.items()}\n",
    "        return self.template.format(**capitalized_kwargs)\n",
    "        "
   ]
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   "cell_type": "markdown",
   "id": "76d1d84d",
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   "source": [
    "We can now see that when we use this, the input variables get formatted."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "id": "eed1ff28",
   "metadata": {},
   "outputs": [],
   "source": [
    "prompt = CustomPromptTemplate(input_variables=[\"foo\"], template=\"Capitalized: {foo}\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "id": "94892a3c",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'Capitalized: LOWERCASE'"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "prompt.format(foo=\"lowercase\")"
   ]
  },
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   "cell_type": "code",
   "execution_count": null,
   "id": "d3d9a7c7",
   "metadata": {},
   "outputs": [],
   "source": []
  }
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