"""Chain for applying constitutional principles to the outputs of another chain."""
from typing import Any, Dict, List, Optional
from langchain_core._api import deprecated
from langchain_core.callbacks import CallbackManagerForChainRun
from langchain_core.language_models import BaseLanguageModel
from langchain_core.prompts import BasePromptTemplate
from langchain.chains.base import Chain
from langchain.chains.constitutional_ai.models import ConstitutionalPrinciple
from langchain.chains.constitutional_ai.principles import PRINCIPLES
from langchain.chains.constitutional_ai.prompts import CRITIQUE_PROMPT, REVISION_PROMPT
from langchain.chains.llm import LLMChain
[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.constitutional_ai.base.ConstitutionalChain.html" # noqa: E501
),
removal="1.0",
)
class ConstitutionalChain(Chain):
"""Chain for applying constitutional principles.
Note: this class is deprecated. See below for a replacement implementation
using LangGraph. The benefits of this implementation are:
- Uses LLM tool calling features instead of parsing string responses;
- 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
from typing import List, Optional, Tuple
from langchain.chains.constitutional_ai.prompts import (
CRITIQUE_PROMPT,
REVISION_PROMPT,
)
from langchain.chains.constitutional_ai.models import ConstitutionalPrinciple
from langchain_core.output_parsers import StrOutputParser
from langchain_core.prompts import ChatPromptTemplate
from langchain_openai import ChatOpenAI
from langgraph.graph import END, START, StateGraph
from typing_extensions import Annotated, TypedDict
llm = ChatOpenAI(model="gpt-4o-mini")
class Critique(TypedDict):
\"\"\"Generate a critique, if needed.\"\"\"
critique_needed: Annotated[bool, ..., "Whether or not a critique is needed."]
critique: Annotated[str, ..., "If needed, the critique."]
critique_prompt = ChatPromptTemplate.from_template(
"Critique this response according to the critique request. "
"If no critique is needed, specify that.\\n\\n"
"Query: {query}\\n\\n"
"Response: {response}\\n\\n"
"Critique request: {critique_request}"
)
revision_prompt = ChatPromptTemplate.from_template(
"Revise this response according to the critique and reivsion request.\\n\\n"
"Query: {query}\\n\\n"
"Response: {response}\\n\\n"
"Critique request: {critique_request}\\n\\n"
"Critique: {critique}\\n\\n"
"If the critique does not identify anything worth changing, ignore the "
"revision request and return 'No revisions needed'. If the critique "
"does identify something worth changing, revise the response based on "
"the revision request.\\n\\n"
"Revision Request: {revision_request}"
)
chain = llm | StrOutputParser()
critique_chain = critique_prompt | llm.with_structured_output(Critique)
revision_chain = revision_prompt | llm | StrOutputParser()
class State(TypedDict):
query: str
constitutional_principles: List[ConstitutionalPrinciple]
initial_response: str
critiques_and_revisions: List[Tuple[str, str]]
response: str
async def generate_response(state: State):
\"\"\"Generate initial response.\"\"\"
response = await chain.ainvoke(state["query"])
return {"response": response, "initial_response": response}
async def critique_and_revise(state: State):
\"\"\"Critique and revise response according to principles.\"\"\"
critiques_and_revisions = []
response = state["initial_response"]
for principle in state["constitutional_principles"]:
critique = await critique_chain.ainvoke(
{
"query": state["query"],
"response": response,
"critique_request": principle.critique_request,
}
)
if critique["critique_needed"]:
revision = await revision_chain.ainvoke(
{
"query": state["query"],
"response": response,
"critique_request": principle.critique_request,
"critique": critique["critique"],
"revision_request": principle.revision_request,
}
)
response = revision
critiques_and_revisions.append((critique["critique"], revision))
else:
critiques_and_revisions.append((critique["critique"], ""))
return {
"critiques_and_revisions": critiques_and_revisions,
"response": response,
}
graph = StateGraph(State)
graph.add_node("generate_response", generate_response)
graph.add_node("critique_and_revise", critique_and_revise)
graph.add_edge(START, "generate_response")
graph.add_edge("generate_response", "critique_and_revise")
graph.add_edge("critique_and_revise", END)
app = graph.compile()
.. code-block:: python
constitutional_principles=[
ConstitutionalPrinciple(
critique_request="Tell if this answer is good.",
revision_request="Give a better answer.",
)
]
query = "What is the meaning of life? Answer in 10 words or fewer."
async for step in app.astream(
{"query": query, "constitutional_principles": constitutional_principles},
stream_mode="values",
):
subset = ["initial_response", "critiques_and_revisions", "response"]
print({k: v for k, v in step.items() if k in subset})
Example:
.. code-block:: python
from langchain_community.llms import OpenAI
from langchain.chains import LLMChain, ConstitutionalChain
from langchain.chains.constitutional_ai.models \
import ConstitutionalPrinciple
llm = OpenAI()
qa_prompt = PromptTemplate(
template="Q: {question} A:",
input_variables=["question"],
)
qa_chain = LLMChain(llm=llm, prompt=qa_prompt)
constitutional_chain = ConstitutionalChain.from_llm(
llm=llm,
chain=qa_chain,
constitutional_principles=[
ConstitutionalPrinciple(
critique_request="Tell if this answer is good.",
revision_request="Give a better answer.",
)
],
)
constitutional_chain.run(question="What is the meaning of life?")
""" # noqa: E501
chain: LLMChain
constitutional_principles: List[ConstitutionalPrinciple]
critique_chain: LLMChain
revision_chain: LLMChain
return_intermediate_steps: bool = False
[docs] @classmethod
def get_principles(
cls, names: Optional[List[str]] = None
) -> List[ConstitutionalPrinciple]:
if names is None:
return list(PRINCIPLES.values())
else:
return [PRINCIPLES[name] for name in names]
[docs] @classmethod
def from_llm(
cls,
llm: BaseLanguageModel,
chain: LLMChain,
critique_prompt: BasePromptTemplate = CRITIQUE_PROMPT,
revision_prompt: BasePromptTemplate = REVISION_PROMPT,
**kwargs: Any,
) -> "ConstitutionalChain":
"""Create a chain from an LLM."""
critique_chain = LLMChain(llm=llm, prompt=critique_prompt)
revision_chain = LLMChain(llm=llm, prompt=revision_prompt)
return cls(
chain=chain,
critique_chain=critique_chain,
revision_chain=revision_chain,
**kwargs,
)
@property
def input_keys(self) -> List[str]:
"""Input keys."""
return self.chain.input_keys
@property
def output_keys(self) -> List[str]:
"""Output keys."""
if self.return_intermediate_steps:
return ["output", "critiques_and_revisions", "initial_output"]
return ["output"]
def _call(
self,
inputs: Dict[str, Any],
run_manager: Optional[CallbackManagerForChainRun] = None,
) -> Dict[str, Any]:
_run_manager = run_manager or CallbackManagerForChainRun.get_noop_manager()
response = self.chain.run(
**inputs,
callbacks=_run_manager.get_child("original"),
)
initial_response = response
input_prompt = self.chain.prompt.format(**inputs)
_run_manager.on_text(
text="Initial response: " + response + "\n\n",
verbose=self.verbose,
color="yellow",
)
critiques_and_revisions = []
for constitutional_principle in self.constitutional_principles:
# Do critique
raw_critique = self.critique_chain.run(
input_prompt=input_prompt,
output_from_model=response,
critique_request=constitutional_principle.critique_request,
callbacks=_run_manager.get_child("critique"),
)
critique = self._parse_critique(
output_string=raw_critique,
).strip()
# if the critique contains "No critique needed", then we're done
# in this case, initial_output is the same as output,
# but we'll keep it for consistency
if "no critique needed" in critique.lower():
critiques_and_revisions.append((critique, ""))
continue
# Do revision
revision = self.revision_chain.run(
input_prompt=input_prompt,
output_from_model=response,
critique_request=constitutional_principle.critique_request,
critique=critique,
revision_request=constitutional_principle.revision_request,
callbacks=_run_manager.get_child("revision"),
).strip()
response = revision
critiques_and_revisions.append((critique, revision))
_run_manager.on_text(
text=f"Applying {constitutional_principle.name}..." + "\n\n",
verbose=self.verbose,
color="green",
)
_run_manager.on_text(
text="Critique: " + critique + "\n\n",
verbose=self.verbose,
color="blue",
)
_run_manager.on_text(
text="Updated response: " + revision + "\n\n",
verbose=self.verbose,
color="yellow",
)
final_output: Dict[str, Any] = {"output": response}
if self.return_intermediate_steps:
final_output["initial_output"] = initial_response
final_output["critiques_and_revisions"] = critiques_and_revisions
return final_output
@staticmethod
def _parse_critique(output_string: str) -> str:
if "Revision request:" not in output_string:
return output_string
output_string = output_string.split("Revision request:")[0]
if "\n\n" in output_string:
output_string = output_string.split("\n\n")[0]
return output_string
