"""Chain that interprets a prompt and executes python code to do math."""
from __future__ import annotations
import math
import re
import warnings
from typing import Any, Dict, List, Optional
from langchain_core._api import deprecated
from langchain_core.callbacks import (
AsyncCallbackManagerForChainRun,
CallbackManagerForChainRun,
)
from langchain_core.language_models import BaseLanguageModel
from langchain_core.prompts import BasePromptTemplate
from pydantic import ConfigDict, model_validator
from langchain.chains.base import Chain
from langchain.chains.llm import LLMChain
from langchain.chains.llm_math.prompt import PROMPT
[docs]
@deprecated(
since="0.2.13",
message=(
"This class is deprecated and will be removed in langchain 1.0. "
"See API reference for replacement: "
"https://api.python.langchain.com/en/latest/chains/langchain.chains.llm_math.base.LLMMathChain.html" # noqa: E501
),
removal="1.0",
)
class LLMMathChain(Chain):
"""Chain that interprets a prompt and executes python code to do math.
Note: this class is deprecated. See below for a replacement implementation
using LangGraph. The benefits of this implementation are:
- Uses LLM tool calling features;
- Support for both token-by-token and step-by-step streaming;
- Support for checkpointing and memory of chat history;
- Easier to modify or extend (e.g., with additional tools, structured responses, etc.)
Install LangGraph with:
.. code-block:: bash
pip install -U langgraph
.. code-block:: python
import math
from typing import Annotated, Sequence
from langchain_core.messages import BaseMessage
from langchain_core.runnables import RunnableConfig
from langchain_core.tools import tool
from langchain_openai import ChatOpenAI
from langgraph.graph import END, StateGraph
from langgraph.graph.message import add_messages
from langgraph.prebuilt.tool_node import ToolNode
import numexpr
from typing_extensions import TypedDict
@tool
def calculator(expression: str) -> str:
\"\"\"Calculate expression using Python's numexpr library.
Expression should be a single line mathematical expression
that solves the problem.
Examples:
"37593 * 67" for "37593 times 67"
"37593**(1/5)" for "37593^(1/5)"
\"\"\"
local_dict = {"pi": math.pi, "e": math.e}
return str(
numexpr.evaluate(
expression.strip(),
global_dict={}, # restrict access to globals
local_dict=local_dict, # add common mathematical functions
)
)
llm = ChatOpenAI(model="gpt-4o-mini", temperature=0)
tools = [calculator]
llm_with_tools = llm.bind_tools(tools, tool_choice="any")
class ChainState(TypedDict):
\"\"\"LangGraph state.\"\"\"
messages: Annotated[Sequence[BaseMessage], add_messages]
async def acall_chain(state: ChainState, config: RunnableConfig):
last_message = state["messages"][-1]
response = await llm_with_tools.ainvoke(state["messages"], config)
return {"messages": [response]}
async def acall_model(state: ChainState, config: RunnableConfig):
response = await llm.ainvoke(state["messages"], config)
return {"messages": [response]}
graph_builder = StateGraph(ChainState)
graph_builder.add_node("call_tool", acall_chain)
graph_builder.add_node("execute_tool", ToolNode(tools))
graph_builder.add_node("call_model", acall_model)
graph_builder.set_entry_point("call_tool")
graph_builder.add_edge("call_tool", "execute_tool")
graph_builder.add_edge("execute_tool", "call_model")
graph_builder.add_edge("call_model", END)
chain = graph_builder.compile()
.. code-block:: python
example_query = "What is 551368 divided by 82"
events = chain.astream(
{"messages": [("user", example_query)]},
stream_mode="values",
)
async for event in events:
event["messages"][-1].pretty_print()
.. code-block:: none
================================ Human Message =================================
What is 551368 divided by 82
================================== Ai Message ==================================
Tool Calls:
calculator (call_MEiGXuJjJ7wGU4aOT86QuGJS)
Call ID: call_MEiGXuJjJ7wGU4aOT86QuGJS
Args:
expression: 551368 / 82
================================= Tool Message =================================
Name: calculator
6724.0
================================== Ai Message ==================================
551368 divided by 82 equals 6724.
Example:
.. code-block:: python
from langchain.chains import LLMMathChain
from langchain_community.llms import OpenAI
llm_math = LLMMathChain.from_llm(OpenAI())
""" # noqa: E501
llm_chain: LLMChain
llm: Optional[BaseLanguageModel] = None
"""[Deprecated] LLM wrapper to use."""
prompt: BasePromptTemplate = PROMPT
"""[Deprecated] Prompt to use to translate to python if necessary."""
input_key: str = "question" #: :meta private:
output_key: str = "answer" #: :meta private:
model_config = ConfigDict(
arbitrary_types_allowed=True,
extra="forbid",
)
@model_validator(mode="before")
@classmethod
def raise_deprecation(cls, values: Dict) -> Any:
try:
import numexpr # noqa: F401
except ImportError:
raise ImportError(
"LLMMathChain requires the numexpr package. "
"Please install it with `pip install numexpr`."
)
if "llm" in values:
warnings.warn(
"Directly instantiating an LLMMathChain with an llm is deprecated. "
"Please instantiate with llm_chain argument or using the from_llm "
"class method."
)
if "llm_chain" not in values and values["llm"] is not None:
prompt = values.get("prompt", PROMPT)
values["llm_chain"] = LLMChain(llm=values["llm"], prompt=prompt)
return values
@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:
import numexpr
try:
local_dict = {"pi": math.pi, "e": math.e}
output = str(
numexpr.evaluate(
expression.strip(),
global_dict={}, # restrict access to globals
local_dict=local_dict, # add common mathematical functions
)
)
except Exception as e:
raise ValueError(
f'LLMMathChain._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_math_chain"
[docs]
@classmethod
def from_llm(
cls,
llm: BaseLanguageModel,
prompt: BasePromptTemplate = PROMPT,
**kwargs: Any,
) -> LLMMathChain:
llm_chain = LLMChain(llm=llm, prompt=prompt)
return cls(llm_chain=llm_chain, **kwargs)
