Source code for langchain.chains.pal.base
"""Implements Program-Aided Language Models.
As in https://arxiv.org/pdf/2211.10435.pdf.
"""
from __future__ import annotations
import warnings
from typing import Any, Dict, List, Optional
from pydantic import Extra, root_validator
from langchain.base_language import BaseLanguageModel
from langchain.callbacks.manager import CallbackManagerForChainRun
from langchain.chains.base import Chain
from langchain.chains.llm import LLMChain
from langchain.chains.pal.colored_object_prompt import COLORED_OBJECT_PROMPT
from langchain.chains.pal.math_prompt import MATH_PROMPT
from langchain.prompts.base import BasePromptTemplate
from langchain.utilities import PythonREPL
[docs]class PALChain(Chain):
    """Implements Program-Aided Language Models."""
    llm_chain: LLMChain
    llm: Optional[BaseLanguageModel] = None
    """[Deprecated]"""
    prompt: BasePromptTemplate = MATH_PROMPT
    """[Deprecated]"""
    stop: str = "\n\n"
    get_answer_expr: str = "print(solution())"
    python_globals: Optional[Dict[str, Any]] = None
    python_locals: Optional[Dict[str, Any]] = None
    output_key: str = "result"  #: :meta private:
    return_intermediate_steps: bool = False
    class Config:
        """Configuration for this pydantic object."""
        extra = Extra.forbid
        arbitrary_types_allowed = True
    @root_validator(pre=True)
    def raise_deprecation(cls, values: Dict) -> Dict:
        if "llm" in values:
            warnings.warn(
                "Directly instantiating an PALChain with an llm is deprecated. "
                "Please instantiate with llm_chain argument or using the one of "
                "the class method constructors from_math_prompt, "
                "from_colored_object_prompt."
            )
            if "llm_chain" not in values and values["llm"] is not None:
                values["llm_chain"] = LLMChain(llm=values["llm"], prompt=MATH_PROMPT)
        return values
    @property
    def input_keys(self) -> List[str]:
        """Return the singular input key.
        :meta private:
        """
        return self.prompt.input_variables
    @property
    def output_keys(self) -> List[str]:
        """Return the singular output key.
        :meta private:
        """
        if not self.return_intermediate_steps:
            return [self.output_key]
        else:
            return [self.output_key, "intermediate_steps"]
    def _call(
        self,
        inputs: Dict[str, Any],
        run_manager: Optional[CallbackManagerForChainRun] = None,
    ) -> Dict[str, str]:
        _run_manager = run_manager or CallbackManagerForChainRun.get_noop_manager()
        code = self.llm_chain.predict(
            stop=[self.stop], callbacks=_run_manager.get_child(), **inputs
        )
        _run_manager.on_text(code, color="green", end="\n", verbose=self.verbose)
        repl = PythonREPL(_globals=self.python_globals, _locals=self.python_locals)
        res = repl.run(code + f"\n{self.get_answer_expr}")
        output = {self.output_key: res.strip()}
        if self.return_intermediate_steps:
            output["intermediate_steps"] = code
        return output
[docs]    @classmethod
    def from_math_prompt(cls, llm: BaseLanguageModel, **kwargs: Any) -> PALChain:
        """Load PAL from math prompt."""
        llm_chain = LLMChain(llm=llm, prompt=MATH_PROMPT)
        return cls(
            llm_chain=llm_chain,
            stop="\n\n",
            get_answer_expr="print(solution())",
            **kwargs,
        )
[docs]    @classmethod
    def from_colored_object_prompt(
        cls, llm: BaseLanguageModel, **kwargs: Any
    ) -> PALChain:
        """Load PAL from colored object prompt."""
        llm_chain = LLMChain(llm=llm, prompt=COLORED_OBJECT_PROMPT)
        return cls(
            llm_chain=llm_chain,
            stop="\n\n\n",
            get_answer_expr="print(answer)",
            **kwargs,
        )
    @property
    def _chain_type(self) -> str:
        return "pal_chain"