Toggle Menu
Prev Up Next

# Source code for langchain.agents.react.base

    """Chain that implements the ReAct paper from https://arxiv.org/pdf/2210.03629.pdf."""
    from __future__ import annotations

    from typing import TYPE_CHECKING, Any, List, Optional, Sequence

    from langchain_core._api import deprecated
    from langchain_core.documents import Document
    from langchain_core.language_models import BaseLanguageModel
    from langchain_core.prompts import BasePromptTemplate
    from langchain_core.pydantic_v1 import Field
    from langchain_core.tools import BaseTool, Tool

    from langchain.agents.agent import Agent, AgentExecutor, AgentOutputParser
    from langchain.agents.agent_types import AgentType
    from langchain.agents.react.output_parser import ReActOutputParser
    from langchain.agents.react.textworld_prompt import TEXTWORLD_PROMPT
    from langchain.agents.react.wiki_prompt import WIKI_PROMPT
    from langchain.agents.utils import validate_tools_single_input

    if TYPE_CHECKING:
        from langchain_community.docstore.base import Docstore

    @deprecated("0.1.0", removal="0.3.0")
    class ReActDocstoreAgent(Agent):
        """Agent for the ReAct chain."""

        output_parser: AgentOutputParser = Field(default_factory=ReActOutputParser)

        @classmethod
        def _get_default_output_parser(cls, **kwargs: Any) -> AgentOutputParser:
            return ReActOutputParser()

        @property
        def _agent_type(self) -> str:
            """Return Identifier of an agent type."""
            return AgentType.REACT_DOCSTORE

        @classmethod
        def create_prompt(cls, tools: Sequence[BaseTool]) -> BasePromptTemplate:
            """Return default prompt."""
            return WIKI_PROMPT

        @classmethod
        def _validate_tools(cls, tools: Sequence[BaseTool]) -> None:
            validate_tools_single_input(cls.__name__, tools)
            super()._validate_tools(tools)
            if len(tools) != 2:
                raise ValueError(f"Exactly two tools must be specified, but got {tools}")
            tool_names = {tool.name for tool in tools}
            if tool_names != {"Lookup", "Search"}:
                raise ValueError(
                    f"Tool names should be Lookup and Search, got {tool_names}"
                )

        @property
        def observation_prefix(self) -> str:
            """Prefix to append the observation with."""
            return "Observation: "

        @property
        def _stop(self) -> List[str]:
            return ["\nObservation:"]

        @property
        def llm_prefix(self) -> str:
            """Prefix to append the LLM call with."""
            return "Thought:"

    @deprecated("0.1.0", removal="0.3.0")
    class DocstoreExplorer:
        """Class to assist with exploration of a document store."""

        def __init__(self, docstore: Docstore):
            """Initialize with a docstore, and set initial document to None."""
            self.docstore = docstore
            self.document: Optional[Document] = None
            self.lookup_str = ""
            self.lookup_index = 0

        def search(self, term: str) -> str:
            """Search for a term in the docstore, and if found save."""
            result = self.docstore.search(term)
            if isinstance(result, Document):
                self.document = result
                return self._summary
            else:
                self.document = None
                return result

        def lookup(self, term: str) -> str:
            """Lookup a term in document (if saved)."""
            if self.document is None:
                raise ValueError("Cannot lookup without a successful search first")
            if term.lower() != self.lookup_str:
                self.lookup_str = term.lower()
                self.lookup_index = 0
            else:
                self.lookup_index += 1
            lookups = [p for p in self._paragraphs if self.lookup_str in p.lower()]
            if len(lookups) == 0:
                return "No Results"
            elif self.lookup_index >= len(lookups):
                return "No More Results"
            else:
                result_prefix = f"(Result {self.lookup_index + 1}/{len(lookups)})"
                return f"{result_prefix} {lookups[self.lookup_index]}"

        @property
        def _summary(self) -> str:
            return self._paragraphs[0]

        @property
        def _paragraphs(self) -> List[str]:
            if self.document is None:
                raise ValueError("Cannot get paragraphs without a document")
            return self.document.page_content.split("\n\n")

    @deprecated("0.1.0", removal="0.3.0")
    class ReActTextWorldAgent(ReActDocstoreAgent):
        """Agent for the ReAct TextWorld chain."""

        @classmethod
        def create_prompt(cls, tools: Sequence[BaseTool]) -> BasePromptTemplate:
            """Return default prompt."""
            return TEXTWORLD_PROMPT

        @classmethod
        def _validate_tools(cls, tools: Sequence[BaseTool]) -> None:
            validate_tools_single_input(cls.__name__, tools)
            super()._validate_tools(tools)
            if len(tools) != 1:
                raise ValueError(f"Exactly one tool must be specified, but got {tools}")
            tool_names = {tool.name for tool in tools}
            if tool_names != {"Play"}:
                raise ValueError(f"Tool name should be Play, got {tool_names}")

    @deprecated("0.1.0", removal="0.3.0")
    class ReActChain(AgentExecutor):
        """[Deprecated] Chain that implements the ReAct paper."""

        def __init__(self, llm: BaseLanguageModel, docstore: Docstore, **kwargs: Any):
            """Initialize with the LLM and a docstore."""
            docstore_explorer = DocstoreExplorer(docstore)
            tools = [
                Tool(
                    name="Search",
                    func=docstore_explorer.search,
                    description="Search for a term in the docstore.",
                ),
                Tool(
                    name="Lookup",
                    func=docstore_explorer.lookup,
                    description="Lookup a term in the docstore.",
                ),
            ]
            agent = ReActDocstoreAgent.from_llm_and_tools(llm, tools)
            super().__init__(agent=agent, tools=tools, **kwargs)