langchain/libs/experimental/langchain_experimental/llm_symbolic_math/base.py

"""Chain that interprets a prompt and executes python code to do symbolic math."""

from __future__ import annotations

import re
from typing import Any, Dict, List, Optional

from langchain.base_language import BaseLanguageModel
from langchain.chains.base import Chain
from langchain.chains.llm import LLMChain
from langchain_core.callbacks.manager import (
    AsyncCallbackManagerForChainRun,
    CallbackManagerForChainRun,
)
from langchain_core.prompts.base import BasePromptTemplate
from pydantic import ConfigDict

from langchain_experimental.llm_symbolic_math.prompt import PROMPT


class LLMSymbolicMathChain(Chain):
    """Chain that interprets a prompt and executes python code to do symbolic math.

    It is based on the sympy library and can be used to evaluate
    mathematical expressions.
    See https://www.sympy.org/ for more information.

    Example:
        .. code-block:: python

            from langchain.chains import LLMSymbolicMathChain
            from langchain_community.llms import OpenAI
            llm_symbolic_math = LLMSymbolicMathChain.from_llm(OpenAI())
    """

    llm_chain: LLMChain
    input_key: str = "question"  #: :meta private:
    output_key: str = "answer"  #: :meta private:

    model_config = ConfigDict(
        arbitrary_types_allowed=True,
        extra="forbid",
    )

    @property
    def input_keys(self) -> List[str]:
        """Expect input key.

        :meta private:
        """
        return [self.input_key]

    @property
    def output_keys(self) -> List[str]:
        """Expect output key.

        :meta private:
        """
        return [self.output_key]

    def _evaluate_expression(self, expression: str) -> str:
        try:
            import sympy
        except ImportError as e:
            raise ImportError(
                "Unable to import sympy, please install it with `pip install sympy`."
            ) from e
        try:
            output = str(sympy.sympify(expression, evaluate=True))
        except Exception as e:
            raise ValueError(
                f'LLMSymbolicMathChain._evaluate("{expression}") raised error: {e}.'
                " Please try again with a valid numerical expression"
            )

        # Remove any leading and trailing brackets from the output
        return re.sub(r"^\[|\]$", "", output)

    def _process_llm_result(
        self, llm_output: str, run_manager: CallbackManagerForChainRun
    ) -> Dict[str, str]:
        run_manager.on_text(llm_output, color="green", verbose=self.verbose)
        llm_output = llm_output.strip()
        text_match = re.search(r"^```text(.*?)```", llm_output, re.DOTALL)
        if text_match:
            expression = text_match.group(1)
            output = self._evaluate_expression(expression)
            run_manager.on_text("\nAnswer: ", verbose=self.verbose)
            run_manager.on_text(output, color="yellow", verbose=self.verbose)
            answer = "Answer: " + output
        elif llm_output.startswith("Answer:"):
            answer = llm_output
        elif "Answer:" in llm_output:
            answer = "Answer: " + llm_output.split("Answer:")[-1]
        else:
            raise ValueError(f"unknown format from LLM: {llm_output}")
        return {self.output_key: answer}

    async def _aprocess_llm_result(
        self,
        llm_output: str,
        run_manager: AsyncCallbackManagerForChainRun,
    ) -> Dict[str, str]:
        await run_manager.on_text(llm_output, color="green", verbose=self.verbose)
        llm_output = llm_output.strip()
        text_match = re.search(r"^```text(.*?)```", llm_output, re.DOTALL)
        if text_match:
            expression = text_match.group(1)
            output = self._evaluate_expression(expression)
            await run_manager.on_text("\nAnswer: ", verbose=self.verbose)
            await run_manager.on_text(output, color="yellow", verbose=self.verbose)
            answer = "Answer: " + output
        elif llm_output.startswith("Answer:"):
            answer = llm_output
        elif "Answer:" in llm_output:
            answer = "Answer: " + llm_output.split("Answer:")[-1]
        else:
            raise ValueError(f"unknown format from LLM: {llm_output}")
        return {self.output_key: answer}

    def _call(
        self,
        inputs: Dict[str, str],
        run_manager: Optional[CallbackManagerForChainRun] = None,
    ) -> Dict[str, str]:
        _run_manager = run_manager or CallbackManagerForChainRun.get_noop_manager()
        _run_manager.on_text(inputs[self.input_key])
        llm_output = self.llm_chain.predict(
            question=inputs[self.input_key],
            stop=["```output"],
            callbacks=_run_manager.get_child(),
        )
        return self._process_llm_result(llm_output, _run_manager)

    async def _acall(
        self,
        inputs: Dict[str, str],
        run_manager: Optional[AsyncCallbackManagerForChainRun] = None,
    ) -> Dict[str, str]:
        _run_manager = run_manager or AsyncCallbackManagerForChainRun.get_noop_manager()
        await _run_manager.on_text(inputs[self.input_key])
        llm_output = await self.llm_chain.apredict(
            question=inputs[self.input_key],
            stop=["```output"],
            callbacks=_run_manager.get_child(),
        )
        return await self._aprocess_llm_result(llm_output, _run_manager)

    @property
    def _chain_type(self) -> str:
        return "llm_symbolic_math_chain"

    @classmethod
    def from_llm(
        cls,
        llm: BaseLanguageModel,
        prompt: BasePromptTemplate = PROMPT,
        **kwargs: Any,
    ) -> LLMSymbolicMathChain:
        llm_chain = LLMChain(llm=llm, prompt=prompt)
        return cls(llm_chain=llm_chain, **kwargs)