"""String distance evaluators based on the RapidFuzz library."""
from enum import Enum
from typing import Any, Callable, Dict, List, Optional
from langchain_core.callbacks.manager import (
AsyncCallbackManagerForChainRun,
CallbackManagerForChainRun,
Callbacks,
)
from langchain_core.utils import pre_init
from pydantic import Field
from langchain.chains.base import Chain
from langchain.evaluation.schema import PairwiseStringEvaluator, StringEvaluator
from langchain.schema import RUN_KEY
def _load_rapidfuzz() -> Any:
"""
Load the RapidFuzz library.
Raises:
ImportError: If the rapidfuzz library is not installed.
Returns:
Any: The rapidfuzz.distance module.
"""
try:
import rapidfuzz
except ImportError:
raise ImportError(
"Please install the rapidfuzz library to use the FuzzyMatchStringEvaluator."
"Please install it with `pip install rapidfuzz`."
)
return rapidfuzz.distance
[docs]
class StringDistance(str, Enum):
"""Distance metric to use.
Attributes:
DAMERAU_LEVENSHTEIN: The Damerau-Levenshtein distance.
LEVENSHTEIN: The Levenshtein distance.
JARO: The Jaro distance.
JARO_WINKLER: The Jaro-Winkler distance.
HAMMING: The Hamming distance.
INDEL: The Indel distance.
"""
DAMERAU_LEVENSHTEIN = "damerau_levenshtein"
LEVENSHTEIN = "levenshtein"
JARO = "jaro"
JARO_WINKLER = "jaro_winkler"
HAMMING = "hamming"
INDEL = "indel"
class _RapidFuzzChainMixin(Chain):
"""Shared methods for the rapidfuzz string distance evaluators."""
distance: StringDistance = Field(default=StringDistance.JARO_WINKLER)
normalize_score: bool = Field(default=True)
"""Whether to normalize the score to a value between 0 and 1.
Applies only to the Levenshtein and Damerau-Levenshtein distances."""
@pre_init
def validate_dependencies(cls, values: Dict[str, Any]) -> Dict[str, Any]:
"""
Validate that the rapidfuzz library is installed.
Args:
values (Dict[str, Any]): The input values.
Returns:
Dict[str, Any]: The validated values.
"""
_load_rapidfuzz()
return values
@property
def output_keys(self) -> List[str]:
"""
Get the output keys.
Returns:
List[str]: The output keys.
"""
return ["score"]
def _prepare_output(self, result: Dict[str, Any]) -> Dict[str, Any]:
"""
Prepare the output dictionary.
Args:
result (Dict[str, Any]): The evaluation results.
Returns:
Dict[str, Any]: The prepared output dictionary.
"""
result = {"score": result["score"]}
if RUN_KEY in result:
result[RUN_KEY] = result[RUN_KEY].dict()
return result
@staticmethod
def _get_metric(distance: str, normalize_score: bool = False) -> Callable:
"""
Get the distance metric function based on the distance type.
Args:
distance (str): The distance type.
Returns:
Callable: The distance metric function.
Raises:
ValueError: If the distance metric is invalid.
"""
from rapidfuzz import distance as rf_distance
module_map: Dict[str, Any] = {
StringDistance.DAMERAU_LEVENSHTEIN: rf_distance.DamerauLevenshtein,
StringDistance.LEVENSHTEIN: rf_distance.Levenshtein,
StringDistance.JARO: rf_distance.Jaro,
StringDistance.JARO_WINKLER: rf_distance.JaroWinkler,
StringDistance.HAMMING: rf_distance.Hamming,
StringDistance.INDEL: rf_distance.Indel,
}
if distance not in module_map:
raise ValueError(
f"Invalid distance metric: {distance}"
f"\nMust be one of: {list(StringDistance)}"
)
module = module_map[distance]
if normalize_score:
return module.normalized_distance
else:
return module.distance
@property
def metric(self) -> Callable:
"""
Get the distance metric function.
Returns:
Callable: The distance metric function.
"""
return _RapidFuzzChainMixin._get_metric(
self.distance, normalize_score=self.normalize_score
)
def compute_metric(self, a: str, b: str) -> float:
"""
Compute the distance between two strings.
Args:
a (str): The first string.
b (str): The second string.
Returns:
float: The distance between the two strings.
"""
return self.metric(a, b)
[docs]
class StringDistanceEvalChain(StringEvaluator, _RapidFuzzChainMixin):
"""Compute string distances between the prediction and the reference.
Examples
----------
>>> from langchain.evaluation import StringDistanceEvalChain
>>> evaluator = StringDistanceEvalChain()
>>> evaluator.evaluate_strings(
prediction="Mindy is the CTO",
reference="Mindy is the CEO",
)
Using the `load_evaluator` function:
>>> from langchain.evaluation import load_evaluator
>>> evaluator = load_evaluator("string_distance")
>>> evaluator.evaluate_strings(
prediction="The answer is three",
reference="three",
)
"""
@property
def requires_input(self) -> bool:
"""
This evaluator does not require input.
"""
return False
@property
def requires_reference(self) -> bool:
"""
This evaluator does not require a reference.
"""
return True
@property
def input_keys(self) -> List[str]:
"""
Get the input keys.
Returns:
List[str]: The input keys.
"""
return ["reference", "prediction"]
@property
def evaluation_name(self) -> str:
"""
Get the evaluation name.
Returns:
str: The evaluation name.
"""
return f"{self.distance.value}_distance"
def _call(
self,
inputs: Dict[str, Any],
run_manager: Optional[CallbackManagerForChainRun] = None,
) -> Dict[str, Any]:
"""
Compute the string distance between the prediction and the reference.
Args:
inputs (Dict[str, Any]): The input values.
run_manager (Optional[CallbackManagerForChainRun]):
The callback manager.
Returns:
Dict[str, Any]: The evaluation results containing the score.
"""
return {"score": self.compute_metric(inputs["reference"], inputs["prediction"])}
async def _acall(
self,
inputs: Dict[str, Any],
run_manager: Optional[AsyncCallbackManagerForChainRun] = None,
) -> Dict[str, Any]:
"""
Asynchronously compute the string distance between the prediction
and the reference.
Args:
inputs (Dict[str, Any]): The input values.
run_manager (Optional[AsyncCallbackManagerForChainRun]:
The callback manager.
Returns:
Dict[str, Any]: The evaluation results containing the score.
"""
return {"score": self.compute_metric(inputs["reference"], inputs["prediction"])}
def _evaluate_strings(
self,
*,
prediction: str,
reference: Optional[str] = None,
input: Optional[str] = None,
callbacks: Callbacks = None,
tags: Optional[List[str]] = None,
metadata: Optional[Dict[str, Any]] = None,
include_run_info: bool = False,
**kwargs: Any,
) -> dict:
"""
Evaluate the string distance between the prediction and the reference.
Args:
prediction (str): The prediction string.
reference (Optional[str], optional): The reference string.
input (Optional[str], optional): The input string.
callbacks (Callbacks, optional): The callbacks to use.
kwargs: Additional keyword arguments.
Returns:
dict: The evaluation results containing the score.
"""
result = self(
inputs={"prediction": prediction, "reference": reference},
callbacks=callbacks,
tags=tags,
metadata=metadata,
include_run_info=include_run_info,
)
return self._prepare_output(result)
async def _aevaluate_strings(
self,
*,
prediction: str,
reference: Optional[str] = None,
input: Optional[str] = None,
callbacks: Callbacks = None,
tags: Optional[List[str]] = None,
metadata: Optional[Dict[str, Any]] = None,
include_run_info: bool = False,
**kwargs: Any,
) -> dict:
"""
Asynchronously evaluate the string distance between the
prediction and the reference.
Args:
prediction (str): The prediction string.
reference (Optional[str], optional): The reference string.
input (Optional[str], optional): The input string.
callbacks (Callbacks, optional): The callbacks to use.
kwargs: Additional keyword arguments.
Returns:
dict: The evaluation results containing the score.
"""
result = await self.acall(
inputs={"prediction": prediction, "reference": reference},
callbacks=callbacks,
tags=tags,
metadata=metadata,
include_run_info=include_run_info,
)
return self._prepare_output(result)
[docs]
class PairwiseStringDistanceEvalChain(PairwiseStringEvaluator, _RapidFuzzChainMixin):
"""Compute string edit distances between two predictions."""
@property
def input_keys(self) -> List[str]:
"""
Get the input keys.
Returns:
List[str]: The input keys.
"""
return ["prediction", "prediction_b"]
@property
def evaluation_name(self) -> str:
"""
Get the evaluation name.
Returns:
str: The evaluation name.
"""
return f"pairwise_{self.distance.value}_distance"
def _call(
self,
inputs: Dict[str, Any],
run_manager: Optional[CallbackManagerForChainRun] = None,
) -> Dict[str, Any]:
"""
Compute the string distance between two predictions.
Args:
inputs (Dict[str, Any]): The input values.
run_manager (CallbackManagerForChainRun , optional):
The callback manager.
Returns:
Dict[str, Any]: The evaluation results containing the score.
"""
return {
"score": self.compute_metric(inputs["prediction"], inputs["prediction_b"])
}
async def _acall(
self,
inputs: Dict[str, Any],
run_manager: Optional[AsyncCallbackManagerForChainRun] = None,
) -> Dict[str, Any]:
"""
Asynchronously compute the string distance between two predictions.
Args:
inputs (Dict[str, Any]): The input values.
run_manager (AsyncCallbackManagerForChainRun , optional):
The callback manager.
Returns:
Dict[str, Any]: The evaluation results containing the score.
"""
return {
"score": self.compute_metric(inputs["prediction"], inputs["prediction_b"])
}
def _evaluate_string_pairs(
self,
*,
prediction: str,
prediction_b: str,
callbacks: Callbacks = None,
tags: Optional[List[str]] = None,
metadata: Optional[Dict[str, Any]] = None,
include_run_info: bool = False,
**kwargs: Any,
) -> dict:
"""
Evaluate the string distance between two predictions.
Args:
prediction (str): The first prediction string.
prediction_b (str): The second prediction string.
callbacks (Callbacks, optional): The callbacks to use.
tags (List[str], optional): Tags to apply to traces.
metadata (Dict[str, Any], optional): Metadata to apply to traces.
kwargs: Additional keyword arguments.
Returns:
dict: The evaluation results containing the score.
"""
result = self(
inputs={"prediction": prediction, "prediction_b": prediction_b},
callbacks=callbacks,
tags=tags,
metadata=metadata,
include_run_info=include_run_info,
)
return self._prepare_output(result)
async def _aevaluate_string_pairs(
self,
*,
prediction: str,
prediction_b: str,
callbacks: Callbacks = None,
tags: Optional[List[str]] = None,
metadata: Optional[Dict[str, Any]] = None,
include_run_info: bool = False,
**kwargs: Any,
) -> dict:
"""
Asynchronously evaluate the string distance between two predictions.
Args:
prediction (str): The first prediction string.
prediction_b (str): The second prediction string.
callbacks (Callbacks, optional): The callbacks to use.
tags (List[str], optional): Tags to apply to traces.
metadata (Dict[str, Any], optional): Metadata to apply to traces.
kwargs: Additional keyword arguments.
Returns:
dict: The evaluation results containing the score.
"""
result = await self.acall(
inputs={"prediction": prediction, "prediction_b": prediction_b},
callbacks=callbacks,
tags=tags,
metadata=metadata,
include_run_info=include_run_info,
)
return self._prepare_output(result)
