from __future__ import annotations
from typing import Any, TypeVar, Union
from langchain_core.exceptions import OutputParserException
from langchain_core.language_models import BaseLanguageModel
from langchain_core.output_parsers import BaseOutputParser, StrOutputParser
from langchain_core.prompt_values import PromptValue
from langchain_core.prompts import BasePromptTemplate, PromptTemplate
from langchain_core.runnables import RunnableSerializable
from pydantic import SkipValidation
from typing_extensions import Annotated, TypedDict
NAIVE_COMPLETION_RETRY = """Prompt:
{prompt}
Completion:
{completion}
Above, the Completion did not satisfy the constraints given in the Prompt.
Please try again:"""
NAIVE_COMPLETION_RETRY_WITH_ERROR = """Prompt:
{prompt}
Completion:
{completion}
Above, the Completion did not satisfy the constraints given in the Prompt.
Details: {error}
Please try again:"""
NAIVE_RETRY_PROMPT = PromptTemplate.from_template(NAIVE_COMPLETION_RETRY)
NAIVE_RETRY_WITH_ERROR_PROMPT = PromptTemplate.from_template(
NAIVE_COMPLETION_RETRY_WITH_ERROR
)
T = TypeVar("T")
[docs]
class RetryOutputParser(BaseOutputParser[T]):
"""Wrap a parser and try to fix parsing errors.
Does this by passing the original prompt and the completion to another
LLM, and telling it the completion did not satisfy criteria in the prompt.
"""
parser: Annotated[BaseOutputParser[T], SkipValidation()]
"""The parser to use to parse the output."""
# Should be an LLMChain but we want to avoid top-level imports from langchain.chains
retry_chain: Union[RunnableSerializable[RetryOutputParserRetryChainInput, str], Any]
"""The RunnableSerializable to use to retry the completion (Legacy: LLMChain)."""
max_retries: int = 1
"""The maximum number of times to retry the parse."""
legacy: bool = True
"""Whether to use the run or arun method of the retry_chain."""
[docs]
@classmethod
def from_llm(
cls,
llm: BaseLanguageModel,
parser: BaseOutputParser[T],
prompt: BasePromptTemplate = NAIVE_RETRY_PROMPT,
max_retries: int = 1,
) -> RetryOutputParser[T]:
"""Create an RetryOutputParser from a language model and a parser.
Args:
llm: llm to use for fixing
parser: parser to use for parsing
prompt: prompt to use for fixing
max_retries: Maximum number of retries to parse.
Returns:
RetryOutputParser
"""
chain = prompt | llm | StrOutputParser()
return cls(parser=parser, retry_chain=chain, max_retries=max_retries)
[docs]
def parse_with_prompt(self, completion: str, prompt_value: PromptValue) -> T:
"""Parse the output of an LLM call using a wrapped parser.
Args:
completion: The chain completion to parse.
prompt_value: The prompt to use to parse the completion.
Returns:
The parsed completion.
"""
retries = 0
while retries <= self.max_retries:
try:
return self.parser.parse(completion)
except OutputParserException as e:
if retries == self.max_retries:
raise e
else:
retries += 1
if self.legacy and hasattr(self.retry_chain, "run"):
completion = self.retry_chain.run(
prompt=prompt_value.to_string(),
completion=completion,
)
else:
completion = self.retry_chain.invoke(
dict(
prompt=prompt_value.to_string(),
completion=completion,
)
)
raise OutputParserException("Failed to parse")
[docs]
async def aparse_with_prompt(self, completion: str, prompt_value: PromptValue) -> T:
"""Parse the output of an LLM call using a wrapped parser.
Args:
completion: The chain completion to parse.
prompt_value: The prompt to use to parse the completion.
Returns:
The parsed completion.
"""
retries = 0
while retries <= self.max_retries:
try:
return await self.parser.aparse(completion)
except OutputParserException as e:
if retries == self.max_retries:
raise e
else:
retries += 1
if self.legacy and hasattr(self.retry_chain, "arun"):
completion = await self.retry_chain.arun(
prompt=prompt_value.to_string(),
completion=completion,
error=repr(e),
)
else:
completion = await self.retry_chain.ainvoke(
dict(
prompt=prompt_value.to_string(),
completion=completion,
)
)
raise OutputParserException("Failed to parse")
[docs]
def parse(self, completion: str) -> T:
raise NotImplementedError(
"This OutputParser can only be called by the `parse_with_prompt` method."
)
@property
def _type(self) -> str:
return "retry"
@property
def OutputType(self) -> type[T]:
return self.parser.OutputType
[docs]
class RetryWithErrorOutputParser(BaseOutputParser[T]):
"""Wrap a parser and try to fix parsing errors.
Does this by passing the original prompt, the completion, AND the error
that was raised to another language model and telling it that the completion
did not work, and raised the given error. Differs from RetryOutputParser
in that this implementation provides the error that was raised back to the
LLM, which in theory should give it more information on how to fix it.
"""
parser: Annotated[BaseOutputParser[T], SkipValidation()]
"""The parser to use to parse the output."""
# Should be an LLMChain but we want to avoid top-level imports from langchain.chains
retry_chain: Union[
RunnableSerializable[RetryWithErrorOutputParserRetryChainInput, str], Any
]
"""The RunnableSerializable to use to retry the completion (Legacy: LLMChain)."""
max_retries: int = 1
"""The maximum number of times to retry the parse."""
legacy: bool = True
"""Whether to use the run or arun method of the retry_chain."""
[docs]
@classmethod
def from_llm(
cls,
llm: BaseLanguageModel,
parser: BaseOutputParser[T],
prompt: BasePromptTemplate = NAIVE_RETRY_WITH_ERROR_PROMPT,
max_retries: int = 1,
) -> RetryWithErrorOutputParser[T]:
"""Create a RetryWithErrorOutputParser from an LLM.
Args:
llm: The LLM to use to retry the completion.
parser: The parser to use to parse the output.
prompt: The prompt to use to retry the completion.
max_retries: The maximum number of times to retry the completion.
Returns:
A RetryWithErrorOutputParser.
"""
chain = prompt | llm | StrOutputParser()
return cls(parser=parser, retry_chain=chain, max_retries=max_retries)
[docs]
def parse_with_prompt(self, completion: str, prompt_value: PromptValue) -> T:
retries = 0
while retries <= self.max_retries:
try:
return self.parser.parse(completion)
except OutputParserException as e:
if retries == self.max_retries:
raise e
else:
retries += 1
if self.legacy and hasattr(self.retry_chain, "run"):
completion = self.retry_chain.run(
prompt=prompt_value.to_string(),
completion=completion,
error=repr(e),
)
else:
completion = self.retry_chain.invoke(
dict(
completion=completion,
prompt=prompt_value.to_string(),
error=repr(e),
)
)
raise OutputParserException("Failed to parse")
[docs]
async def aparse_with_prompt(self, completion: str, prompt_value: PromptValue) -> T:
retries = 0
while retries <= self.max_retries:
try:
return await self.parser.aparse(completion)
except OutputParserException as e:
if retries == self.max_retries:
raise e
else:
retries += 1
if self.legacy and hasattr(self.retry_chain, "arun"):
completion = await self.retry_chain.arun(
prompt=prompt_value.to_string(),
completion=completion,
error=repr(e),
)
else:
completion = await self.retry_chain.ainvoke(
dict(
prompt=prompt_value.to_string(),
completion=completion,
error=repr(e),
)
)
raise OutputParserException("Failed to parse")
[docs]
def parse(self, completion: str) -> T:
raise NotImplementedError(
"This OutputParser can only be called by the `parse_with_prompt` method."
)
@property
def _type(self) -> str:
return "retry_with_error"
@property
def OutputType(self) -> type[T]:
return self.parser.OutputType
