langchain/docs/extras/guides/evaluation/comparison/custom.ipynb
2023-07-24 16:31:20 -07:00

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"# Custom Pairwise Evaluator\n",
"\n",
"You can make your own pairwise string evaluators by inheriting from `PairwiseStringEvaluator` class and overwriting the `_evaluate_string_pairs` method (and the `_aevaluate_string_pairs` method if you want to use the evaluator asynchronously).\n",
"\n",
"In this example, you will make a simple custom evaluator that just returns whether the first prediction has more whitespace tokenized 'words' than the second.\n",
"\n",
"You can check out the reference docs for the [PairwiseStringEvaluator interface](https://api.python.langchain.com/en/latest/evaluation/langchain.evaluation.schema.PairwiseStringEvaluator.html#langchain.evaluation.schema.PairwiseStringEvaluator) for more info.\n"
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"from typing import Optional, Any\n",
"from langchain.evaluation import PairwiseStringEvaluator\n",
"\n",
"\n",
"class LengthComparisonPairwiseEvalutor(PairwiseStringEvaluator):\n",
" \"\"\"\n",
" Custom evaluator to compare two strings.\n",
" \"\"\"\n",
"\n",
" def _evaluate_string_pairs(\n",
" self,\n",
" *,\n",
" prediction: str,\n",
" prediction_b: str,\n",
" reference: Optional[str] = None,\n",
" input: Optional[str] = None,\n",
" **kwargs: Any,\n",
" ) -> dict:\n",
" score = int(len(prediction.split()) > len(prediction_b.split()))\n",
" return {\"score\": score}"
]
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"{'score': 1}"
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"source": [
"evaluator = LengthComparisonPairwiseEvalutor()\n",
"\n",
"evaluator.evaluate_string_pairs(\n",
" prediction=\"The quick brown fox jumped over the lazy dog.\",\n",
" prediction_b=\"The quick brown fox jumped over the dog.\",\n",
")"
]
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"## LLM-Based Example\n",
"\n",
"That example was simple to illustrate the API, but it wasn't very useful in practice. Below, use an LLM with some custom instructions to form a simple preference scorer similar to the built-in [PairwiseStringEvalChain](https://api.python.langchain.com/en/latest/evaluation/langchain.evaluation.comparison.eval_chain.PairwiseStringEvalChain.html#langchain.evaluation.comparison.eval_chain.PairwiseStringEvalChain). We will use `ChatAnthropic` for the evaluator chain."
]
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"source": [
"# %pip install anthropic\n",
"# %env ANTHROPIC_API_KEY=YOUR_API_KEY"
]
},
{
"cell_type": "code",
"execution_count": 4,
"id": "b6e978ab-48f1-47ff-9506-e13b1a50be6e",
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"from typing import Optional, Any\n",
"from langchain.evaluation import PairwiseStringEvaluator\n",
"from langchain.chat_models import ChatAnthropic\n",
"from langchain.chains import LLMChain\n",
"\n",
"\n",
"class CustomPreferenceEvaluator(PairwiseStringEvaluator):\n",
" \"\"\"\n",
" Custom evaluator to compare two strings using a custom LLMChain.\n",
" \"\"\"\n",
"\n",
" def __init__(self) -> None:\n",
" llm = ChatAnthropic(model=\"claude-2\", temperature=0)\n",
" self.eval_chain = LLMChain.from_string(\n",
" llm,\n",
" \"\"\"Which option is preferred? Do not take order into account. Evaluate based on accuracy and helpfulness. If neither is preferred, respond with C. Provide your reasoning, then finish with Preference: A/B/C\n",
"\n",
"Input: How do I get the path of the parent directory in python 3.8?\n",
"Option A: You can use the following code:\n",
"```python\n",
"import os\n",
"\n",
"os.path.dirname(os.path.dirname(os.path.abspath(__file__)))\n",
"```\n",
"Option B: You can use the following code:\n",
"```python\n",
"from pathlib import Path\n",
"Path(__file__).absolute().parent\n",
"```\n",
"Reasoning: Both options return the same result. However, since option B is more concise and easily understand, it is preferred.\n",
"Preference: B\n",
"\n",
"Which option is preferred? Do not take order into account. Evaluate based on accuracy and helpfulness. If neither is preferred, respond with C. Provide your reasoning, then finish with Preference: A/B/C\n",
"Input: {input}\n",
"Option A: {prediction}\n",
"Option B: {prediction_b}\n",
"Reasoning:\"\"\",\n",
" )\n",
"\n",
" @property\n",
" def requires_input(self) -> bool:\n",
" return True\n",
"\n",
" @property\n",
" def requires_reference(self) -> bool:\n",
" return False\n",
"\n",
" def _evaluate_string_pairs(\n",
" self,\n",
" *,\n",
" prediction: str,\n",
" prediction_b: str,\n",
" reference: Optional[str] = None,\n",
" input: Optional[str] = None,\n",
" **kwargs: Any,\n",
" ) -> dict:\n",
" result = self.eval_chain(\n",
" {\n",
" \"input\": input,\n",
" \"prediction\": prediction,\n",
" \"prediction_b\": prediction_b,\n",
" \"stop\": [\"Which option is preferred?\"],\n",
" },\n",
" **kwargs,\n",
" )\n",
"\n",
" response_text = result[\"text\"]\n",
" reasoning, preference = response_text.split(\"Preference:\", maxsplit=1)\n",
" preference = preference.strip()\n",
" score = 1.0 if preference == \"A\" else (0.0 if preference == \"B\" else None)\n",
" return {\"reasoning\": reasoning.strip(), \"value\": preference, \"score\": score}"
]
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"evaluator = CustomPreferenceEvaluator()"
]
},
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"{'reasoning': 'Option B is preferred over option A for importing from a relative directory, because it is more straightforward and concise.\\n\\nOption A uses the importlib module, which allows importing a module by specifying the full name as a string. While this works, it is less clear compared to option B.\\n\\nOption B directly imports from the relative path using dot notation, which clearly shows that it is a relative import. This is the recommended way to do relative imports in Python.\\n\\nIn summary, option B is more accurate and helpful as it uses the standard Python relative import syntax.',\n",
" 'value': 'B',\n",
" 'score': 0.0}"
]
},
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"source": [
"evaluator.evaluate_string_pairs(\n",
" input=\"How do I import from a relative directory?\",\n",
" prediction=\"use importlib! importlib.import_module('.my_package', '.')\",\n",
" prediction_b=\"from .sibling import foo\",\n",
")"
]
},
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"name": "stdout",
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"text": [
"CustomPreferenceEvaluator requires an input string.\n"
]
}
],
"source": [
"# Setting requires_input to return True adds additional validation to avoid returning a grade when insufficient data is provided to the chain.\n",
"\n",
"try:\n",
" evaluator.evaluate_string_pairs(\n",
" prediction=\"use importlib! importlib.import_module('.my_package', '.')\",\n",
" prediction_b=\"from .sibling import foo\",\n",
" )\n",
"except ValueError as e:\n",
" print(e)"
]
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