"""Chain that combines documents by stuffing into context."""
from typing import Any, Dict, List, Optional, Tuple
from langchain_core._api import deprecated
from langchain_core.callbacks import Callbacks
from langchain_core.documents import Document
from langchain_core.language_models import LanguageModelLike
from langchain_core.output_parsers import BaseOutputParser, StrOutputParser
from langchain_core.prompts import BasePromptTemplate, format_document
from langchain_core.runnables import Runnable, RunnablePassthrough
from pydantic import ConfigDict, Field, model_validator
from langchain.chains.combine_documents.base import (
DEFAULT_DOCUMENT_PROMPT,
DEFAULT_DOCUMENT_SEPARATOR,
DOCUMENTS_KEY,
BaseCombineDocumentsChain,
_validate_prompt,
)
from langchain.chains.llm import LLMChain
[docs]
def create_stuff_documents_chain(
llm: LanguageModelLike,
prompt: BasePromptTemplate,
*,
output_parser: Optional[BaseOutputParser] = None,
document_prompt: Optional[BasePromptTemplate] = None,
document_separator: str = DEFAULT_DOCUMENT_SEPARATOR,
document_variable_name: str = DOCUMENTS_KEY,
) -> Runnable[Dict[str, Any], Any]:
"""Create a chain for passing a list of Documents to a model.
Args:
llm: Language model.
prompt: Prompt template. Must contain input variable "context" (override by
setting document_variable), which will be used for passing in the formatted documents.
output_parser: Output parser. Defaults to StrOutputParser.
document_prompt: Prompt used for formatting each document into a string. Input
variables can be "page_content" or any metadata keys that are in all
documents. "page_content" will automatically retrieve the
`Document.page_content`, and all other inputs variables will be
automatically retrieved from the `Document.metadata` dictionary. Default to
a prompt that only contains `Document.page_content`.
document_separator: String separator to use between formatted document strings.
document_variable_name: Variable name to use for the formatted documents in the prompt.
Defaults to "context".
Returns:
An LCEL Runnable. The input is a dictionary that must have a "context" key that
maps to a List[Document], and any other input variables expected in the prompt.
The Runnable return type depends on output_parser used.
Example:
.. code-block:: python
# pip install -U langchain langchain-community
from langchain_community.chat_models import ChatOpenAI
from langchain_core.documents import Document
from langchain_core.prompts import ChatPromptTemplate
from langchain.chains.combine_documents import create_stuff_documents_chain
prompt = ChatPromptTemplate.from_messages(
[("system", "What are everyone's favorite colors:\\n\\n{context}")]
)
llm = ChatOpenAI(model="gpt-3.5-turbo")
chain = create_stuff_documents_chain(llm, prompt)
docs = [
Document(page_content="Jesse loves red but not yellow"),
Document(page_content = "Jamal loves green but not as much as he loves orange")
]
chain.invoke({"context": docs})
""" # noqa: E501
_validate_prompt(prompt, document_variable_name)
_document_prompt = document_prompt or DEFAULT_DOCUMENT_PROMPT
_output_parser = output_parser or StrOutputParser()
def format_docs(inputs: dict) -> str:
return document_separator.join(
format_document(doc, _document_prompt)
for doc in inputs[document_variable_name]
)
return (
RunnablePassthrough.assign(**{document_variable_name: format_docs}).with_config(
run_name="format_inputs"
)
| prompt
| llm
| _output_parser
).with_config(run_name="stuff_documents_chain")
[docs]
@deprecated(
since="0.2.13",
removal="1.0",
message=(
"This class is deprecated. Use the `create_stuff_documents_chain` constructor "
"instead. See migration guide here: "
"https://python.langchain.com/docs/versions/migrating_chains/stuff_docs_chain/" # noqa: E501
),
)
class StuffDocumentsChain(BaseCombineDocumentsChain):
"""Chain that combines documents by stuffing into context.
This chain takes a list of documents and first combines them into a single string.
It does this by formatting each document into a string with the `document_prompt`
and then joining them together with `document_separator`. It then adds that new
string to the inputs with the variable name set by `document_variable_name`.
Those inputs are then passed to the `llm_chain`.
Example:
.. code-block:: python
from langchain.chains import StuffDocumentsChain, LLMChain
from langchain_core.prompts import PromptTemplate
from langchain_community.llms import OpenAI
# This controls how each document will be formatted. Specifically,
# it will be passed to `format_document` - see that function for more
# details.
document_prompt = PromptTemplate(
input_variables=["page_content"],
template="{page_content}"
)
document_variable_name = "context"
llm = OpenAI()
# The prompt here should take as an input variable the
# `document_variable_name`
prompt = PromptTemplate.from_template(
"Summarize this content: {context}"
)
llm_chain = LLMChain(llm=llm, prompt=prompt)
chain = StuffDocumentsChain(
llm_chain=llm_chain,
document_prompt=document_prompt,
document_variable_name=document_variable_name
)
"""
llm_chain: LLMChain
"""LLM chain which is called with the formatted document string,
along with any other inputs."""
document_prompt: BasePromptTemplate = Field(
default_factory=lambda: DEFAULT_DOCUMENT_PROMPT
)
"""Prompt to use to format each document, gets passed to `format_document`."""
document_variable_name: str
"""The variable name in the llm_chain to put the documents in.
If only one variable in the llm_chain, this need not be provided."""
document_separator: str = "\n\n"
"""The string with which to join the formatted documents"""
model_config = ConfigDict(
arbitrary_types_allowed=True,
extra="forbid",
)
@model_validator(mode="before")
@classmethod
def get_default_document_variable_name(cls, values: Dict) -> Any:
"""Get default document variable name, if not provided.
If only one variable is present in the llm_chain.prompt,
we can infer that the formatted documents should be passed in
with this variable name.
"""
llm_chain_variables = values["llm_chain"].prompt.input_variables
if "document_variable_name" not in values:
if len(llm_chain_variables) == 1:
values["document_variable_name"] = llm_chain_variables[0]
else:
raise ValueError(
"document_variable_name must be provided if there are "
"multiple llm_chain_variables"
)
else:
if values["document_variable_name"] not in llm_chain_variables:
raise ValueError(
f"document_variable_name {values['document_variable_name']} was "
f"not found in llm_chain input_variables: {llm_chain_variables}"
)
return values
@property
def input_keys(self) -> List[str]:
extra_keys = [
k for k in self.llm_chain.input_keys if k != self.document_variable_name
]
return super().input_keys + extra_keys
def _get_inputs(self, docs: List[Document], **kwargs: Any) -> dict:
"""Construct inputs from kwargs and docs.
Format and then join all the documents together into one input with name
`self.document_variable_name`. Also pluck any additional variables
from **kwargs.
Args:
docs: List of documents to format and then join into single input
**kwargs: additional inputs to chain, will pluck any other required
arguments from here.
Returns:
dictionary of inputs to LLMChain
"""
# Format each document according to the prompt
doc_strings = [format_document(doc, self.document_prompt) for doc in docs]
# Join the documents together to put them in the prompt.
inputs = {
k: v
for k, v in kwargs.items()
if k in self.llm_chain.prompt.input_variables
}
inputs[self.document_variable_name] = self.document_separator.join(doc_strings)
return inputs
[docs]
def prompt_length(self, docs: List[Document], **kwargs: Any) -> Optional[int]:
"""Return the prompt length given the documents passed in.
This can be used by a caller to determine whether passing in a list
of documents would exceed a certain prompt length. This useful when
trying to ensure that the size of a prompt remains below a certain
context limit.
Args:
docs: List[Document], a list of documents to use to calculate the
total prompt length.
Returns:
Returns None if the method does not depend on the prompt length,
otherwise the length of the prompt in tokens.
"""
inputs = self._get_inputs(docs, **kwargs)
prompt = self.llm_chain.prompt.format(**inputs)
return self.llm_chain._get_num_tokens(prompt)
[docs]
def combine_docs(
self, docs: List[Document], callbacks: Callbacks = None, **kwargs: Any
) -> Tuple[str, dict]:
"""Stuff all documents into one prompt and pass to LLM.
Args:
docs: List of documents to join together into one variable
callbacks: Optional callbacks to pass along
**kwargs: additional parameters to use to get inputs to LLMChain.
Returns:
The first element returned is the single string output. The second
element returned is a dictionary of other keys to return.
"""
inputs = self._get_inputs(docs, **kwargs)
# Call predict on the LLM.
return self.llm_chain.predict(callbacks=callbacks, **inputs), {}
[docs]
async def acombine_docs(
self, docs: List[Document], callbacks: Callbacks = None, **kwargs: Any
) -> Tuple[str, dict]:
"""Async stuff all documents into one prompt and pass to LLM.
Args:
docs: List of documents to join together into one variable
callbacks: Optional callbacks to pass along
**kwargs: additional parameters to use to get inputs to LLMChain.
Returns:
The first element returned is the single string output. The second
element returned is a dictionary of other keys to return.
"""
inputs = self._get_inputs(docs, **kwargs)
# Call predict on the LLM.
return await self.llm_chain.apredict(callbacks=callbacks, **inputs), {}
@property
def _chain_type(self) -> str:
return "stuff_documents_chain"
