"""Use tenacity to retry the embedding call."""
    retry_decorator = _create_retry_decorator(embeddings)
    @retry_decorator
    def _embed_with_retry(**kwargs: Any) -> Any:
        return embeddings.client.create(**kwargs)
    return _embed_with_retry(**kwargs)
[docs]class OpenAIEmbeddings(BaseModel, Embeddings):
    """Wrapper around OpenAI embedding models.
    To use, you should have the ``openai`` python package installed, and the
    environment variable ``OPENAI_API_KEY`` set with your API key or pass it
    as a named parameter to the constructor.
    Example:
        .. code-block:: python
            from langchain.embeddings import OpenAIEmbeddings
            openai = OpenAIEmbeddings(openai_api_key="my-api-key")
    In order to use the library with Microsoft Azure endpoints, you need to set
    the OPENAI_API_TYPE, OPENAI_API_BASE, OPENAI_API_KEY and optionally and
    API_VERSION.
    The OPENAI_API_TYPE must be set to 'azure' and the others correspond to
    the properties of your endpoint.
    In addition, the deployment name must be passed as the model parameter.
    Example:
        .. code-block:: python
            import os
            os.environ["OPENAI_API_TYPE"] = "azure"
            os.environ["OPENAI_API_BASE"] = "https://<your-endpoint.openai.azure.com/"
            os.environ["OPENAI_API_KEY"] = "your AzureOpenAI key"
            from langchain.embeddings.openai import OpenAIEmbeddings
            embeddings = OpenAIEmbeddings(
                deployment="your-embeddings-deployment-name",
                model="your-embeddings-model-name"
            )
            text = "This is a test query."
            query_result = embeddings.embed_query(text)


text = "This is a test query."
            query_result = embeddings.embed_query(text)
    """
    client: Any  #: :meta private:
    model: str = "text-embedding-ada-002"
    deployment: str = model  # to support Azure OpenAI Service custom deployment names
    embedding_ctx_length: int = 8191
    openai_api_key: Optional[str] = None
    openai_organization: Optional[str] = None
    allowed_special: Union[Literal["all"], Set[str]] = set()
    disallowed_special: Union[Literal["all"], Set[str], Tuple[()]] = "all"
    chunk_size: int = 1000
    """Maximum number of texts to embed in each batch"""
    max_retries: int = 6
    """Maximum number of retries to make when generating."""
    class Config:
        """Configuration for this pydantic object."""
        extra = Extra.forbid
    @root_validator()
    def validate_environment(cls, values: Dict) -> Dict:
        """Validate that api key and python package exists in environment."""
        openai_api_key = get_from_dict_or_env(
            values, "openai_api_key", "OPENAI_API_KEY"
        )
        openai_organization = get_from_dict_or_env(
            values,
            "openai_organization",
            "OPENAI_ORGANIZATION",
            default="",
        )
        try:
            import openai
            openai.api_key = openai_api_key
            if openai_organization:
                openai.organization = openai_organization
            values["client"] = openai.Embedding
        except ImportError:
            raise ValueError(
                "Could not import openai python package. "
                "Please install it with `pip install openai`."
            )


"Please install it with `pip install openai`."
            )
        return values
    # please refer to
    # https://github.com/openai/openai-cookbook/blob/main/examples/Embedding_long_inputs.ipynb
    def _get_len_safe_embeddings(
        self, texts: List[str], *, engine: str, chunk_size: Optional[int] = None
    ) -> List[List[float]]:
        embeddings: List[List[float]] = [[] for i in range(len(texts))]
        try:
            import tiktoken
            tokens = []
            indices = []
            encoding = tiktoken.model.encoding_for_model(self.model)
            for i, text in enumerate(texts):
                # replace newlines, which can negatively affect performance.
                text = text.replace("\n", " ")
                token = encoding.encode(
                    text,
                    allowed_special=self.allowed_special,
                    disallowed_special=self.disallowed_special,
                )
                for j in range(0, len(token), self.embedding_ctx_length):
                    tokens += [token[j : j + self.embedding_ctx_length]]
                    indices += [i]
            batched_embeddings = []
            _chunk_size = chunk_size or self.chunk_size
            for i in range(0, len(tokens), _chunk_size):
                response = embed_with_retry(
                    self,
                    input=tokens[i : i + _chunk_size],
                    engine=self.deployment,
                )
                batched_embeddings += [r["embedding"] for r in response["data"]]
            results: List[List[List[float]]] = [[] for i in range(len(texts))]
            lens: List[List[int]] = [[] for i in range(len(texts))]
            for i in range(len(indices)):
                results[indices[i]].append(batched_embeddings[i])


results[indices[i]].append(batched_embeddings[i])
                lens[indices[i]].append(len(batched_embeddings[i]))
            for i in range(len(texts)):
                average = np.average(results[i], axis=0, weights=lens[i])
                embeddings[i] = (average / np.linalg.norm(average)).tolist()
            return embeddings
        except ImportError:
            raise ValueError(
                "Could not import tiktoken python package. "
                "This is needed in order to for OpenAIEmbeddings. "
                "Please install it with `pip install tiktoken`."
            )
    def _embedding_func(self, text: str, *, engine: str) -> List[float]:
        """Call out to OpenAI's embedding endpoint."""
        # handle large input text
        if self.embedding_ctx_length > 0:
            return self._get_len_safe_embeddings([text], engine=engine)[0]
        else:
            # replace newlines, which can negatively affect performance.
            text = text.replace("\n", " ")
            return embed_with_retry(self, input=[text], engine=engine)["data"][0][
                "embedding"
            ]
[docs]    def embed_documents(
        self, texts: List[str], chunk_size: Optional[int] = 0
    ) -> List[List[float]]:
        """Call out to OpenAI's embedding endpoint for embedding search docs.
        Args:
            texts: The list of texts to embed.
            chunk_size: The chunk size of embeddings. If None, will use the chunk size
                specified by the class.
        Returns:
            List of embeddings, one for each text.
        """
        # handle batches of large input text
        if self.embedding_ctx_length > 0:


# handle batches of large input text
        if self.embedding_ctx_length > 0:
            return self._get_len_safe_embeddings(texts, engine=self.deployment)
        else:
            results = []
            _chunk_size = chunk_size or self.chunk_size
            for i in range(0, len(texts), _chunk_size):
                response = embed_with_retry(
                    self,
                    input=texts[i : i + _chunk_size],
                    engine=self.deployment,
                )
                results += [r["embedding"] for r in response["data"]]
            return results
[docs]    def embed_query(self, text: str) -> List[float]:
        """Call out to OpenAI's embedding endpoint for embedding query text.
        Args:
            text: The text to embed.
        Returns:
            Embedding for the text.
        """
        embedding = self._embedding_func(text, engine=self.deployment)
        return embedding
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


Source code for langchain.embeddings.self_hosted_hugging_face
"""Wrapper around HuggingFace embedding models for self-hosted remote hardware."""
import importlib
import logging
from typing import Any, Callable, List, Optional
from langchain.embeddings.self_hosted import SelfHostedEmbeddings
DEFAULT_MODEL_NAME = "sentence-transformers/all-mpnet-base-v2"
DEFAULT_INSTRUCT_MODEL = "hkunlp/instructor-large"
DEFAULT_EMBED_INSTRUCTION = "Represent the document for retrieval: "
DEFAULT_QUERY_INSTRUCTION = (
    "Represent the question for retrieving supporting documents: "
)
logger = logging.getLogger(__name__)
def _embed_documents(client: Any, *args: Any, **kwargs: Any) -> List[List[float]]:
    """Inference function to send to the remote hardware.
    Accepts a sentence_transformer model_id and
    returns a list of embeddings for each document in the batch.
    """
    return client.encode(*args, **kwargs)
def load_embedding_model(model_id: str, instruct: bool = False, device: int = 0) -> Any:
    """Load the embedding model."""
    if not instruct:
        import sentence_transformers
        client = sentence_transformers.SentenceTransformer(model_id)
    else:
        from InstructorEmbedding import INSTRUCTOR
        client = INSTRUCTOR(model_id)
    if importlib.util.find_spec("torch") is not None:
        import torch
        cuda_device_count = torch.cuda.device_count()
        if device < -1 or (device >= cuda_device_count):
            raise ValueError(
                f"Got device=={device}, "
                f"device is required to be within [-1, {cuda_device_count})"
            )
        if device < 0 and cuda_device_count > 0:
            logger.warning(


if device < 0 and cuda_device_count > 0:
            logger.warning(
                "Device has %d GPUs available. "
                "Provide device={deviceId} to `from_model_id` to use available"
                "GPUs for execution. deviceId is -1 for CPU and "
                "can be a positive integer associated with CUDA device id.",
                cuda_device_count,
            )
        client = client.to(device)
    return client
[docs]class SelfHostedHuggingFaceEmbeddings(SelfHostedEmbeddings):
    """Runs sentence_transformers embedding models on self-hosted remote hardware.
    Supported hardware includes auto-launched instances on AWS, GCP, Azure,
    and Lambda, as well as servers specified
    by IP address and SSH credentials (such as on-prem, or another cloud
    like Paperspace, Coreweave, etc.).
    To use, you should have the ``runhouse`` python package installed.
    Example:
        .. code-block:: python
            from langchain.embeddings import SelfHostedHuggingFaceEmbeddings
            import runhouse as rh
            model_name = "sentence-transformers/all-mpnet-base-v2"
            gpu = rh.cluster(name="rh-a10x", instance_type="A100:1")
            hf = SelfHostedHuggingFaceEmbeddings(model_name=model_name, hardware=gpu)
    """
    client: Any  #: :meta private:
    model_id: str = DEFAULT_MODEL_NAME
    """Model name to use."""
    model_reqs: List[str] = ["./", "sentence_transformers", "torch"]
    """Requirements to install on hardware to inference the model."""
    hardware: Any
    """Remote hardware to send the inference function to."""
    model_load_fn: Callable = load_embedding_model


model_load_fn: Callable = load_embedding_model
    """Function to load the model remotely on the server."""
    load_fn_kwargs: Optional[dict] = None
    """Key word arguments to pass to the model load function."""
    inference_fn: Callable = _embed_documents
    """Inference function to extract the embeddings."""
    def __init__(self, **kwargs: Any):
        """Initialize the remote inference function."""
        load_fn_kwargs = kwargs.pop("load_fn_kwargs", {})
        load_fn_kwargs["model_id"] = load_fn_kwargs.get("model_id", DEFAULT_MODEL_NAME)
        load_fn_kwargs["instruct"] = load_fn_kwargs.get("instruct", False)
        load_fn_kwargs["device"] = load_fn_kwargs.get("device", 0)
        super().__init__(load_fn_kwargs=load_fn_kwargs, **kwargs)
[docs]class SelfHostedHuggingFaceInstructEmbeddings(SelfHostedHuggingFaceEmbeddings):
    """Runs InstructorEmbedding embedding models on self-hosted remote hardware.
    Supported hardware includes auto-launched instances on AWS, GCP, Azure,
    and Lambda, as well as servers specified
    by IP address and SSH credentials (such as on-prem, or another
    cloud like Paperspace, Coreweave, etc.).
    To use, you should have the ``runhouse`` python package installed.
    Example:
        .. code-block:: python
            from langchain.embeddings import SelfHostedHuggingFaceInstructEmbeddings
            import runhouse as rh
            model_name = "hkunlp/instructor-large"
            gpu = rh.cluster(name='rh-a10x', instance_type='A100:1')
            hf = SelfHostedHuggingFaceInstructEmbeddings(
                model_name=model_name, hardware=gpu)
    """


model_name=model_name, hardware=gpu)
    """
    model_id: str = DEFAULT_INSTRUCT_MODEL
    """Model name to use."""
    embed_instruction: str = DEFAULT_EMBED_INSTRUCTION
    """Instruction to use for embedding documents."""
    query_instruction: str = DEFAULT_QUERY_INSTRUCTION
    """Instruction to use for embedding query."""
    model_reqs: List[str] = ["./", "InstructorEmbedding", "torch"]
    """Requirements to install on hardware to inference the model."""
    def __init__(self, **kwargs: Any):
        """Initialize the remote inference function."""
        load_fn_kwargs = kwargs.pop("load_fn_kwargs", {})
        load_fn_kwargs["model_id"] = load_fn_kwargs.get(
            "model_id", DEFAULT_INSTRUCT_MODEL
        )
        load_fn_kwargs["instruct"] = load_fn_kwargs.get("instruct", True)
        load_fn_kwargs["device"] = load_fn_kwargs.get("device", 0)
        super().__init__(load_fn_kwargs=load_fn_kwargs, **kwargs)
[docs]    def embed_documents(self, texts: List[str]) -> List[List[float]]:
        """Compute doc embeddings using a HuggingFace instruct model.
        Args:
            texts: The list of texts to embed.
        Returns:
            List of embeddings, one for each text.
        """
        instruction_pairs = []
        for text in texts:
            instruction_pairs.append([self.embed_instruction, text])
        embeddings = self.client(self.pipeline_ref, instruction_pairs)
        return embeddings.tolist()
[docs]    def embed_query(self, text: str) -> List[float]:
        """Compute query embeddings using a HuggingFace instruct model.
        Args:
            text: The text to embed.
        Returns:
            Embeddings for the text.


text: The text to embed.
        Returns:
            Embeddings for the text.
        """
        instruction_pair = [self.query_instruction, text]
        embedding = self.client(self.pipeline_ref, [instruction_pair])[0]
        return embedding.tolist()
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


Source code for langchain.embeddings.fake
from typing import List
import numpy as np
from pydantic import BaseModel
from langchain.embeddings.base import Embeddings
[docs]class FakeEmbeddings(Embeddings, BaseModel):
    size: int
    def _get_embedding(self) -> List[float]:
        return list(np.random.normal(size=self.size))
[docs]    def embed_documents(self, texts: List[str]) -> List[List[float]]:
        return [self._get_embedding() for _ in texts]
[docs]    def embed_query(self, text: str) -> List[float]:
        return self._get_embedding()
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


Source code for langchain.embeddings.cohere
"""Wrapper around Cohere embedding models."""
from typing import Any, Dict, List, Optional
from pydantic import BaseModel, Extra, root_validator
from langchain.embeddings.base import Embeddings
from langchain.utils import get_from_dict_or_env
[docs]class CohereEmbeddings(BaseModel, Embeddings):
    """Wrapper around Cohere embedding models.
    To use, you should have the ``cohere`` python package installed, and the
    environment variable ``COHERE_API_KEY`` set with your API key or pass it
    as a named parameter to the constructor.
    Example:
        .. code-block:: python
            from langchain.embeddings import CohereEmbeddings
            cohere = CohereEmbeddings(model="medium", cohere_api_key="my-api-key")
    """
    client: Any  #: :meta private:
    model: str = "large"
    """Model name to use."""
    truncate: Optional[str] = None
    """Truncate embeddings that are too long from start or end ("NONE"|"START"|"END")"""
    cohere_api_key: Optional[str] = None
    class Config:
        """Configuration for this pydantic object."""
        extra = Extra.forbid
    @root_validator()
    def validate_environment(cls, values: Dict) -> Dict:
        """Validate that api key and python package exists in environment."""
        cohere_api_key = get_from_dict_or_env(
            values, "cohere_api_key", "COHERE_API_KEY"
        )
        try:
            import cohere
            values["client"] = cohere.Client(cohere_api_key)
        except ImportError:
            raise ValueError(
                "Could not import cohere python package. "


raise ValueError(
                "Could not import cohere python package. "
                "Please install it with `pip install cohere`."
            )
        return values
[docs]    def embed_documents(self, texts: List[str]) -> List[List[float]]:
        """Call out to Cohere's embedding endpoint.
        Args:
            texts: The list of texts to embed.
        Returns:
            List of embeddings, one for each text.
        """
        embeddings = self.client.embed(
            model=self.model, texts=texts, truncate=self.truncate
        ).embeddings
        return [list(map(float, e)) for e in embeddings]
[docs]    def embed_query(self, text: str) -> List[float]:
        """Call out to Cohere's embedding endpoint.
        Args:
            text: The text to embed.
        Returns:
            Embeddings for the text.
        """
        embedding = self.client.embed(
            model=self.model, texts=[text], truncate=self.truncate
        ).embeddings[0]
        return list(map(float, embedding))
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


Source code for langchain.embeddings.self_hosted
"""Running custom embedding models on self-hosted remote hardware."""
from typing import Any, Callable, List
from pydantic import Extra
from langchain.embeddings.base import Embeddings
from langchain.llms import SelfHostedPipeline
def _embed_documents(pipeline: Any, *args: Any, **kwargs: Any) -> List[List[float]]:
    """Inference function to send to the remote hardware.
    Accepts a sentence_transformer model_id and
    returns a list of embeddings for each document in the batch.
    """
    return pipeline(*args, **kwargs)
[docs]class SelfHostedEmbeddings(SelfHostedPipeline, Embeddings):
    """Runs custom embedding models on self-hosted remote hardware.
    Supported hardware includes auto-launched instances on AWS, GCP, Azure,
    and Lambda, as well as servers specified
    by IP address and SSH credentials (such as on-prem, or another
    cloud like Paperspace, Coreweave, etc.).
    To use, you should have the ``runhouse`` python package installed.
    Example using a model load function:
        .. code-block:: python
            from langchain.embeddings import SelfHostedEmbeddings
            from transformers import AutoModelForCausalLM, AutoTokenizer, pipeline
            import runhouse as rh
            gpu = rh.cluster(name="rh-a10x", instance_type="A100:1")
            def get_pipeline():
                model_id = "facebook/bart-large"
                tokenizer = AutoTokenizer.from_pretrained(model_id)
                model = AutoModelForCausalLM.from_pretrained(model_id)
                return pipeline("feature-extraction", model=model, tokenizer=tokenizer)
            embeddings = SelfHostedEmbeddings(
                model_load_fn=get_pipeline,
                hardware=gpu


model_load_fn=get_pipeline,
                hardware=gpu
                model_reqs=["./", "torch", "transformers"],
            )
    Example passing in a pipeline path:
        .. code-block:: python
            from langchain.embeddings import SelfHostedHFEmbeddings
            import runhouse as rh
            from transformers import pipeline
            gpu = rh.cluster(name="rh-a10x", instance_type="A100:1")
            pipeline = pipeline(model="bert-base-uncased", task="feature-extraction")
            rh.blob(pickle.dumps(pipeline),
                path="models/pipeline.pkl").save().to(gpu, path="models")
            embeddings = SelfHostedHFEmbeddings.from_pipeline(
                pipeline="models/pipeline.pkl",
                hardware=gpu,
                model_reqs=["./", "torch", "transformers"],
            )
    """
    inference_fn: Callable = _embed_documents
    """Inference function to extract the embeddings on the remote hardware."""
    inference_kwargs: Any = None
    """Any kwargs to pass to the model's inference function."""
    class Config:
        """Configuration for this pydantic object."""
        extra = Extra.forbid
[docs]    def embed_documents(self, texts: List[str]) -> List[List[float]]:
        """Compute doc embeddings using a HuggingFace transformer model.
        Args:
            texts: The list of texts to embed.s
        Returns:
            List of embeddings, one for each text.
        """
        texts = list(map(lambda x: x.replace("\n", " "), texts))
        embeddings = self.client(self.pipeline_ref, texts)
        if not isinstance(embeddings, list):
            return embeddings.tolist()
        return embeddings
[docs]    def embed_query(self, text: str) -> List[float]:


[docs]    def embed_query(self, text: str) -> List[float]:
        """Compute query embeddings using a HuggingFace transformer model.
        Args:
            text: The text to embed.
        Returns:
            Embeddings for the text.
        """
        text = text.replace("\n", " ")
        embeddings = self.client(self.pipeline_ref, text)
        if not isinstance(embeddings, list):
            return embeddings.tolist()
        return embeddings
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


Source code for langchain.embeddings.tensorflow_hub
"""Wrapper around TensorflowHub embedding models."""
from typing import Any, List
from pydantic import BaseModel, Extra
from langchain.embeddings.base import Embeddings
DEFAULT_MODEL_URL = "https://tfhub.dev/google/universal-sentence-encoder-multilingual/3"
[docs]class TensorflowHubEmbeddings(BaseModel, Embeddings):
    """Wrapper around tensorflow_hub embedding models.
    To use, you should have the ``tensorflow_text`` python package installed.
    Example:
        .. code-block:: python
            from langchain.embeddings import TensorflowHubEmbeddings
            url = "https://tfhub.dev/google/universal-sentence-encoder-multilingual/3"
            tf = TensorflowHubEmbeddings(model_url=url)
    """
    embed: Any  #: :meta private:
    model_url: str = DEFAULT_MODEL_URL
    """Model name to use."""
    def __init__(self, **kwargs: Any):
        """Initialize the tensorflow_hub and tensorflow_text."""
        super().__init__(**kwargs)
        try:
            import tensorflow_hub
            import tensorflow_text  # noqa
            self.embed = tensorflow_hub.load(self.model_url)
        except ImportError as e:
            raise ValueError(
                "Could not import some python packages." "Please install them."
            ) from e
    class Config:
        """Configuration for this pydantic object."""
        extra = Extra.forbid
[docs]    def embed_documents(self, texts: List[str]) -> List[List[float]]:
        """Compute doc embeddings using a TensorflowHub embedding model.
        Args:
            texts: The list of texts to embed.
        Returns:
            List of embeddings, one for each text.
        """


Returns:
            List of embeddings, one for each text.
        """
        texts = list(map(lambda x: x.replace("\n", " "), texts))
        embeddings = self.embed(texts).numpy()
        return embeddings.tolist()
[docs]    def embed_query(self, text: str) -> List[float]:
        """Compute query embeddings using a TensorflowHub embedding model.
        Args:
            text: The text to embed.
        Returns:
            Embeddings for the text.
        """
        text = text.replace("\n", " ")
        embedding = self.embed(text).numpy()[0]
        return embedding.tolist()
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


Source code for langchain.embeddings.sagemaker_endpoint
"""Wrapper around Sagemaker InvokeEndpoint API."""
from typing import Any, Dict, List, Optional
from pydantic import BaseModel, Extra, root_validator
from langchain.embeddings.base import Embeddings
from langchain.llms.sagemaker_endpoint import ContentHandlerBase
[docs]class SagemakerEndpointEmbeddings(BaseModel, Embeddings):
    """Wrapper around custom Sagemaker Inference Endpoints.
    To use, you must supply the endpoint name from your deployed
    Sagemaker model & the region where it is deployed.
    To authenticate, the AWS client uses the following methods to
    automatically load credentials:
    https://boto3.amazonaws.com/v1/documentation/api/latest/guide/credentials.html
    If a specific credential profile should be used, you must pass
    the name of the profile from the ~/.aws/credentials file that is to be used.
    Make sure the credentials / roles used have the required policies to
    access the Sagemaker endpoint.
    See: https://docs.aws.amazon.com/IAM/latest/UserGuide/access_policies.html
    """
    """
    Example:
        .. code-block:: python
            from langchain.embeddings import SagemakerEndpointEmbeddings
            endpoint_name = (
                "my-endpoint-name"
            )
            region_name = (
                "us-west-2"
            )
            credentials_profile_name = (
                "default"
            )
            se = SagemakerEndpointEmbeddings(
                endpoint_name=endpoint_name,
                region_name=region_name,
                credentials_profile_name=credentials_profile_name
            )
    """
    client: Any  #: :meta private:
    endpoint_name: str = ""
    """The name of the endpoint from the deployed Sagemaker model.


"""The name of the endpoint from the deployed Sagemaker model.
    Must be unique within an AWS Region."""
    region_name: str = ""
    """The aws region where the Sagemaker model is deployed, eg. `us-west-2`."""
    credentials_profile_name: Optional[str] = None
    """The name of the profile in the ~/.aws/credentials or ~/.aws/config files, which
    has either access keys or role information specified.
    If not specified, the default credential profile or, if on an EC2 instance,
    credentials from IMDS will be used.
    See: https://boto3.amazonaws.com/v1/documentation/api/latest/guide/credentials.html
    """
    content_handler: ContentHandlerBase
    """The content handler class that provides an input and
    output transform functions to handle formats between LLM
    and the endpoint.
    """
    """
     Example:
        .. code-block:: python

        from langchain.llms.sagemaker_endpoint import ContentHandlerBase
        class ContentHandler(ContentHandlerBase):
                content_type = "application/json"
                accepts = "application/json"
                def transform_input(self, prompt: str, model_kwargs: Dict) -> bytes:
                    input_str = json.dumps({prompt: prompt, **model_kwargs})
                    return input_str.encode('utf-8')

                def transform_output(self, output: bytes) -> str:
                    response_json = json.loads(output.read().decode("utf-8"))
                    return response_json[0]["generated_text"]
    """
    model_kwargs: Optional[Dict] = None
    """Key word arguments to pass to the model."""
    endpoint_kwargs: Optional[Dict] = None
    """Optional attributes passed to the invoke_endpoint


endpoint_kwargs: Optional[Dict] = None
    """Optional attributes passed to the invoke_endpoint
    function. See `boto3`_. docs for more info.
    .. _boto3: <https://boto3.amazonaws.com/v1/documentation/api/latest/index.html>
    """
    class Config:
        """Configuration for this pydantic object."""
        extra = Extra.forbid
        arbitrary_types_allowed = True
    @root_validator()
    def validate_environment(cls, values: Dict) -> Dict:
        """Validate that AWS credentials to and python package exists in environment."""
        try:
            import boto3
            try:
                if values["credentials_profile_name"] is not None:
                    session = boto3.Session(
                        profile_name=values["credentials_profile_name"]
                    )
                else:
                    # use default credentials
                    session = boto3.Session()
                values["client"] = session.client(
                    "sagemaker-runtime", region_name=values["region_name"]
                )
            except Exception as e:
                raise ValueError(
                    "Could not load credentials to authenticate with AWS client. "
                    "Please check that credentials in the specified "
                    "profile name are valid."
                ) from e
        except ImportError:
            raise ValueError(
                "Could not import boto3 python package. "
                "Please install it with `pip install boto3`."
            )
        return values
    def _embedding_func(self, texts: List[str]) -> List[float]:
        """Call out to SageMaker Inference embedding endpoint."""
        # replace newlines, which can negatively affect performance.
        texts = list(map(lambda x: x.replace("\n", " "), texts))
        _model_kwargs = self.model_kwargs or {}
        _endpoint_kwargs = self.endpoint_kwargs or {}


_endpoint_kwargs = self.endpoint_kwargs or {}
        body = self.content_handler.transform_input(texts, _model_kwargs)
        content_type = self.content_handler.content_type
        accepts = self.content_handler.accepts
        # send request
        try:
            response = self.client.invoke_endpoint(
                EndpointName=self.endpoint_name,
                Body=body,
                ContentType=content_type,
                Accept=accepts,
                **_endpoint_kwargs,
            )
        except Exception as e:
            raise ValueError(f"Error raised by inference endpoint: {e}")
        return self.content_handler.transform_output(response["Body"])
[docs]    def embed_documents(
        self, texts: List[str], chunk_size: int = 64
    ) -> List[List[float]]:
        """Compute doc embeddings using a SageMaker Inference Endpoint.
        Args:
            texts: The list of texts to embed.
            chunk_size: The chunk size defines how many input texts will
                be grouped together as request. If None, will use the
                chunk size specified by the class.
        Returns:
            List of embeddings, one for each text.
        """
        results = []
        _chunk_size = len(texts) if chunk_size > len(texts) else chunk_size
        for i in range(0, len(texts), _chunk_size):
            response = self._embedding_func(texts[i : i + _chunk_size])
            results.append(response)
        return results
[docs]    def embed_query(self, text: str) -> List[float]:
        """Compute query embeddings using a SageMaker inference endpoint.
        Args:
            text: The text to embed.
        Returns:
            Embeddings for the text.
        """
        return self._embedding_func([text])
By Harrison Chase


"""
        return self._embedding_func([text])
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


.rst
.pdf
Chains
Chains#
Note
Conceptual Guide
Using an LLM in isolation is fine for some simple applications,
but many more complex ones require chaining LLMs - either with each other or with other experts.
LangChain provides a standard interface for Chains, as well as some common implementations of chains for ease of use.
The following sections of documentation are provided:
Getting Started: A getting started guide for chains, to get you up and running quickly.
How-To Guides: A collection of how-to guides. These highlight how to use various types of chains.
Reference: API reference documentation for all Chain classes.
previous
Redis Chat Message History
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Getting Started
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  Last updated on Apr 21, 2023.


.rst
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Agents
 Contents
Go Deeper
Agents#
Note
Conceptual Guide
Some applications will require not just a predetermined chain of calls to LLMs/other tools,
but potentially an unknown chain that depends on the user’s input.
In these types of chains, there is a “agent” which has access to a suite of tools.
Depending on the user input, the agent can then decide which, if any, of these tools to call.
In this section of documentation, we first start with a Getting Started notebook to cover how to use all things related to agents in an end-to-end manner.
We then split the documentation into the following sections:
Tools
An overview of the various tools LangChain supports.
Agents
An overview of the different agent types.
Toolkits
An overview of toolkits, and examples of the different ones LangChain supports.
Agent Executor
An overview of the Agent Executor class and examples of how to use it.
Go Deeper#
Tools
Agents
Toolkits
Agent Executors
previous
Chains
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Getting Started
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  Last updated on Apr 21, 2023.


.rst
.pdf
Memory
Memory#
Note
Conceptual Guide
By default, Chains and Agents are stateless,
meaning that they treat each incoming query independently (as are the underlying LLMs and chat models).
In some applications (chatbots being a GREAT example) it is highly important
to remember previous interactions, both at a short term but also at a long term level.
The concept of “Memory” exists to do exactly that.
LangChain provides memory components in two forms.
First, LangChain provides helper utilities for managing and manipulating previous chat messages.
These are designed to be modular and useful regardless of how they are used.
Secondly, LangChain provides easy ways to incorporate these utilities into chains.
The following sections of documentation are provided:
Getting Started: An overview of how to get started with different types of memory.
How-To Guides: A collection of how-to guides. These highlight different types of memory, as well as how to use memory in chains.
Memory
Getting Started
How-To Guides
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Weaviate Hybrid Search
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.rst
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Indexes
 Contents
Go Deeper
Indexes#
Note
Conceptual Guide
Indexes refer to ways to structure documents so that LLMs can best interact with them.
This module contains utility functions for working with documents, different types of indexes, and then examples for using those indexes in chains.
The most common way that indexes are used in chains is in a “retrieval” step.
This step refers to taking a user’s query and returning the most relevant documents.
We draw this distinction because (1) an index can be used for other things besides retrieval, and (2) retrieval can use other logic besides an index to find relevant documents.
We therefore have a concept of a “Retriever” interface - this is the interface that most chains work with.
Most of the time when we talk about indexes and retrieval we are talking about indexing and retrieving unstructured data (like text documents).
For interacting with structured data (SQL tables, etc) or APIs, please see the corresponding use case sections for links to relevant functionality.
The primary index and retrieval types supported by LangChain are currently centered around vector databases, and therefore
a lot of the functionality we dive deep on those topics.
For an overview of everything related to this, please see the below notebook for getting started:
Getting Started
We then provide a deep dive on the four main components.
Document Loaders
How to load documents from a variety of sources.
Text Splitters
An overview of the abstractions and implementions around splitting text.
VectorStores
An overview of VectorStores and the many integrations LangChain provides.
Retrievers
An overview of Retrievers and the implementations LangChain provides.
Go Deeper#
Document Loaders
Text Splitters
Vectorstores
Retrievers
previous
Structured Output Parser
next
Getting Started
 Contents

Go Deeper


previous
Structured Output Parser
next
Getting Started
 Contents

Go Deeper
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  Last updated on Apr 21, 2023.


.rst
.pdf
Models
 Contents
Go Deeper
Models#
Note
Conceptual Guide
This section of the documentation deals with different types of models that are used in LangChain.
On this page we will go over the model types at a high level,
but we have individual pages for each model type.
The pages contain more detailed “how-to” guides for working with that model,
as well as a list of different model providers.
LLMs
Large Language Models (LLMs) are the first type of models we cover.
These models take a text string as input, and return a text string as output.
Chat Models
Chat Models are the second type of models we cover.
These models are usually backed by a language model, but their APIs are more structured.
Specifically, these models take a list of Chat Messages as input, and return a Chat Message.
Text Embedding Models
The third type of models we cover are text embedding models.
These models take text as input and return a list of floats.
Go Deeper#
LLMs
Chat Models
Text Embedding Models
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Quickstart Guide
next
LLMs
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  Last updated on Apr 21, 2023.


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Prompts
 Contents
Go Deeper
Prompts#
Note
Conceptual Guide
The new way of programming models is through prompts.
A “prompt” refers to the input to the model.
This input is rarely hard coded, but rather is often constructed from multiple components.
A PromptTemplate is responsible for the construction of this input.
LangChain provides several classes and functions to make constructing and working with prompts easy.
This section of documentation is split into four sections:
LLM Prompt Templates
How to use PromptTemplates to prompt Language Models.
Chat Prompt Templates
How to use PromptTemplates to prompt Chat Models.
Example Selectors
Often times it is useful to include examples in prompts.
These examples can be hardcoded, but it is often more powerful if they are dynamically selected.
This section goes over example selection.
Output Parsers
Language models (and Chat Models) output text.
But many times you may want to get more structured information than just text back.
This is where output parsers come in.
Output Parsers are responsible for (1) instructing the model how output should be formatted,
(2) parsing output into the desired formatting (including retrying if necessary).
Go Deeper#
Prompt Templates
Chat Prompt Template
Example Selectors
Output Parsers
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TensorflowHub
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Prompt Templates
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.rst
.pdf
Prompt Templates
Prompt Templates#
Note
Conceptual Guide
Language models take text as input - that text is commonly referred to as a prompt.
Typically this is not simply a hardcoded string but rather a combination of a template, some examples, and user input.
LangChain provides several classes and functions to make constructing and working with prompts easy.
The following sections of documentation are provided:
Getting Started: An overview of all the functionality LangChain provides for working with and constructing prompts.
How-To Guides: A collection of how-to guides. These highlight how to accomplish various objectives with our prompt class.
Reference: API reference documentation for all prompt classes.
previous
Prompts
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Getting Started
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  Last updated on Apr 21, 2023.


.rst
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Output Parsers
Output Parsers#
Note
Conceptual Guide
Language models output text. But many times you may want to get more structured information than just text back. This is where output parsers come in.
Output parsers are classes that help structure language model responses. There are two main methods an output parser must implement:
get_format_instructions() -> str: A method which returns a string containing instructions for how the output of a language model should be formatted.
parse(str) -> Any: A method which takes in a string (assumed to be the response from a language model) and parses it into some structure.
And then one optional one:
parse_with_prompt(str) -> Any: A method which takes in a string (assumed to be the response from a language model) and a prompt (assumed to the prompt that generated such a response) and parses it into some structure. The prompt is largely provided in the event the OutputParser wants to retry or fix the output in some way, and needs information from the prompt to do so.
To start, we recommend familiarizing yourself with the Getting Started section
Output Parsers
After that, we provide deep dives on all the different types of output parsers.
CommaSeparatedListOutputParser
OutputFixingParser
PydanticOutputParser
RetryOutputParser
Structured Output Parser
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Similarity ExampleSelector
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Output Parsers
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Chat Prompt Template
Chat Prompt Template#
Chat Models takes a list of chat messages as input - this list commonly referred to as a prompt.
Typically this is not simply a hardcoded list of messages but rather a combination of a template, some examples, and user input.
LangChain provides several classes and functions to make constructing and working with prompts easy.
from langchain.prompts import (
    ChatPromptTemplate,
    PromptTemplate,
    SystemMessagePromptTemplate,
    AIMessagePromptTemplate,
    HumanMessagePromptTemplate,
)
from langchain.schema import (
    AIMessage,
    HumanMessage,
    SystemMessage
)
You can make use of templating by using a MessagePromptTemplate. You can build a ChatPromptTemplate from one or more MessagePromptTemplates. You can use ChatPromptTemplate’s format_prompt – this returns a PromptValue, which you can convert to a string or Message object, depending on whether you want to use the formatted value as input to an llm or chat model.
For convenience, there is a from_template method exposed on the template. If you were to use this template, this is what it would look like:
template="You are a helpful assistant that translates {input_language} to {output_language}."
system_message_prompt = SystemMessagePromptTemplate.from_template(template)
human_template="{text}"
human_message_prompt = HumanMessagePromptTemplate.from_template(human_template)
chat_prompt = ChatPromptTemplate.from_messages([system_message_prompt, human_message_prompt])
# get a chat completion from the formatted messages
chat_prompt.format_prompt(input_language="English", output_language="French", text="I love programming.").to_messages()
[SystemMessage(content='You are a helpful assistant that translates English to French.', additional_kwargs={}),
 HumanMessage(content='I love programming.', additional_kwargs={})]


HumanMessage(content='I love programming.', additional_kwargs={})]
If you wanted to construct the MessagePromptTemplate more directly, you could create a PromptTemplate outside and then pass it in, eg:
prompt=PromptTemplate(
    template="You are a helpful assistant that translates {input_language} to {output_language}.",
    input_variables=["input_language", "output_language"],
)
system_message_prompt = SystemMessagePromptTemplate(prompt=prompt)
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Example Selector
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Example Selectors
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Example Selectors
Example Selectors#
Note
Conceptual Guide
If you have a large number of examples, you may need to select which ones to include in the prompt. The ExampleSelector is the class responsible for doing so.
The base interface is defined as below:
class BaseExampleSelector(ABC):
    """Interface for selecting examples to include in prompts."""
    @abstractmethod
    def select_examples(self, input_variables: Dict[str, str]) -> List[dict]:
        """Select which examples to use based on the inputs."""
The only method it needs to expose is a select_examples method. This takes in the input variables and then returns a list of examples. It is up to each specific implementation as to how those examples are selected. Let’s take a look at some below.
See below for a list of example selectors.
How to create a custom example selector
LengthBased ExampleSelector
Maximal Marginal Relevance ExampleSelector
NGram Overlap ExampleSelector
Similarity ExampleSelector
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Chat Prompt Template
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How to create a custom example selector
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How-To Guides
How-To Guides#
If you’re new to the library, you may want to start with the Quickstart.
The user guide here shows more advanced workflows and how to use the library in different ways.
How to create a custom prompt template
How to create a prompt template that uses few shot examples
How to work with partial Prompt Templates
How to serialize prompts
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Getting Started
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How to create a custom prompt template
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.md
.pdf
Getting Started
 Contents
What is a prompt template?
Create a prompt template
Load a prompt template from LangChainHub
Pass few shot examples to a prompt template
Select examples for a prompt template
Getting Started#
In this tutorial, we will learn about:
what a prompt template is, and why it is needed,
how to create a prompt template,
how to pass few shot examples to a prompt template,
how to select examples for a prompt template.
What is a prompt template?#
A prompt template refers to a reproducible way to generate a prompt. It contains a text string (“the template”), that can take in a set of parameters from the end user and generate a prompt.
The prompt template may contain:
instructions to the language model,
a set of few shot examples to help the language model generate a better response,
a question to the language model.
The following code snippet contains an example of a prompt template:
from langchain import PromptTemplate
template = """
I want you to act as a naming consultant for new companies.
Here are some examples of good company names:
- search engine, Google
- social media, Facebook
- video sharing, YouTube
The name should be short, catchy and easy to remember.
What is a good name for a company that makes {product}?
"""
prompt = PromptTemplate(
    input_variables=["product"],
    template=template,
)
Create a prompt template#
You can create simple hardcoded prompts using the PromptTemplate class. Prompt templates can take any number of input variables, and can be formatted to generate a prompt.
from langchain import PromptTemplate
# An example prompt with no input variables
no_input_prompt = PromptTemplate(input_variables=[], template="Tell me a joke.")
no_input_prompt.format()
# -> "Tell me a joke."


no_input_prompt.format()
# -> "Tell me a joke."
# An example prompt with one input variable
one_input_prompt = PromptTemplate(input_variables=["adjective"], template="Tell me a {adjective} joke.")
one_input_prompt.format(adjective="funny")
# -> "Tell me a funny joke."
# An example prompt with multiple input variables
multiple_input_prompt = PromptTemplate(
    input_variables=["adjective", "content"],
    template="Tell me a {adjective} joke about {content}."
)
multiple_input_prompt.format(adjective="funny", content="chickens")
# -> "Tell me a funny joke about chickens."
You can create custom prompt templates that format the prompt in any way you want. For more information, see Custom Prompt Templates.
Note
Currently, the template should be formatted as a Python f-string. We also support Jinja2 templates (see Using Jinja templates). In the future, we will support more templating languages such as Mako.
Load a prompt template from LangChainHub#
LangChainHub contains a collection of prompts which can be loaded directly via LangChain.
from langchain.prompts import load_prompt
prompt = load_prompt("lc://prompts/conversation/prompt.json")
prompt.format(history="", input="What is 1 + 1?")
You can read more about LangChainHub and the prompts available with it here.
Pass few shot examples to a prompt template#
Few shot examples are a set of examples that can be used to help the language model generate a better response.
To generate a prompt with few shot examples, you can use the FewShotPromptTemplate. This class takes in a PromptTemplate and a list of few shot examples. It then formats the prompt template with the few shot examples.
In this example, we’ll create a prompt to generate word antonyms.


In this example, we’ll create a prompt to generate word antonyms.
from langchain import PromptTemplate, FewShotPromptTemplate
# First, create the list of few shot examples.
examples = [
    {"word": "happy", "antonym": "sad"},
    {"word": "tall", "antonym": "short"},
]
# Next, we specify the template to format the examples we have provided.
# We use the `PromptTemplate` class for this.
example_formatter_template = """
Word: {word}
Antonym: {antonym}\n
"""
example_prompt = PromptTemplate(
    input_variables=["word", "antonym"],
    template=example_formatter_template,
)
# Finally, we create the `FewShotPromptTemplate` object.
few_shot_prompt = FewShotPromptTemplate(
    # These are the examples we want to insert into the prompt.
    examples=examples,
    # This is how we want to format the examples when we insert them into the prompt.
    example_prompt=example_prompt,
    # The prefix is some text that goes before the examples in the prompt.
    # Usually, this consists of intructions.
    prefix="Give the antonym of every input",
    # The suffix is some text that goes after the examples in the prompt.
    # Usually, this is where the user input will go
    suffix="Word: {input}\nAntonym:",
    # The input variables are the variables that the overall prompt expects.
    input_variables=["input"],
    # The example_separator is the string we will use to join the prefix, examples, and suffix together with.
    example_separator="\n\n",
)
# We can now generate a prompt using the `format` method.
print(few_shot_prompt.format(input="big"))


print(few_shot_prompt.format(input="big"))
# -> Give the antonym of every input
# ->
# -> Word: happy
# -> Antonym: sad
# ->
# -> Word: tall
# -> Antonym: short
# ->
# -> Word: big
# -> Antonym:
Select examples for a prompt template#
If you have a large number of examples, you can use the ExampleSelector to select a subset of examples that will be most informative for the Language Model. This will help you generate a prompt that is more likely to generate a good response.
Below, we’ll use the LengthBasedExampleSelector, which selects examples based on the length of the input. This is useful when you are worried about constructing a prompt that will go over the length of the context window. For longer inputs, it will select fewer examples to include, while for shorter inputs it will select more.
We’ll continue with the example from the previous section, but this time we’ll use the LengthBasedExampleSelector to select the examples.
from langchain.prompts.example_selector import LengthBasedExampleSelector
# These are a lot of examples of a pretend task of creating antonyms.
examples = [
    {"word": "happy", "antonym": "sad"},
    {"word": "tall", "antonym": "short"},
    {"word": "energetic", "antonym": "lethargic"},
    {"word": "sunny", "antonym": "gloomy"},
    {"word": "windy", "antonym": "calm"},
]
# We'll use the `LengthBasedExampleSelector` to select the examples.
example_selector = LengthBasedExampleSelector(
    # These are the examples is has available to choose from.
    examples=examples,


# These are the examples is has available to choose from.
    examples=examples,
    # This is the PromptTemplate being used to format the examples.
    example_prompt=example_prompt,
    # This is the maximum length that the formatted examples should be.
    # Length is measured by the get_text_length function below.
    max_length=25,
)
# We can now use the `example_selector` to create a `FewShotPromptTemplate`.
dynamic_prompt = FewShotPromptTemplate(
    # We provide an ExampleSelector instead of examples.
    example_selector=example_selector,
    example_prompt=example_prompt,
    prefix="Give the antonym of every input",
    suffix="Word: {input}\nAntonym:",
    input_variables=["input"],
    example_separator="\n\n",
)
# We can now generate a prompt using the `format` method.
print(dynamic_prompt.format(input="big"))
# -> Give the antonym of every input
# ->
# -> Word: happy
# -> Antonym: sad
# ->
# -> Word: tall
# -> Antonym: short
# ->
# -> Word: energetic
# -> Antonym: lethargic
# ->
# -> Word: sunny
# -> Antonym: gloomy
# ->
# -> Word: windy
# -> Antonym: calm
# ->
# -> Word: big
# -> Antonym:
In contrast, if we provide a very long input, the LengthBasedExampleSelector will select fewer examples to include in the prompt.
long_string = "big and huge and massive and large and gigantic and tall and much much much much much bigger than everything else"
print(dynamic_prompt.format(input=long_string))
# -> Give the antonym of every input
# -> Word: happy
# -> Antonym: sad


# -> Word: happy
# -> Antonym: sad
# ->
# -> Word: big and huge and massive and large and gigantic and tall and much much much much much bigger than everything else
# -> Antonym:
LangChain comes with a few example selectors that you can use. For more details on how to use them, see Example Selectors.
You can create custom example selectors that select examples based on any criteria you want. For more details on how to do this, see Creating a custom example selector.
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Prompt Templates
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How-To Guides
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What is a prompt template?
Create a prompt template
Load a prompt template from LangChainHub
Pass few shot examples to a prompt template
Select examples for a prompt template
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  Last updated on Apr 21, 2023.


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How to work with partial Prompt Templates
 Contents
Partial With Strings
Partial With Functions
How to work with partial Prompt Templates#
A prompt template is a class with a .format method which takes in a key-value map and returns a string (a prompt) to pass to the language model. Like other methods, it can make sense to “partial” a prompt template - eg pass in a subset of the required values, as to create a new prompt template which expects only the remaining subset of values.
LangChain supports this in two ways: we allow for partially formatted prompts (1) with string values, (2) with functions that return string values. These two different ways support different use cases. In the documentation below we go over the motivations for both use cases as well as how to do it in LangChain.
Partial With Strings#
One common use case for wanting to partial a prompt template is if you get some of the variables before others. For example, suppose you have a prompt template that requires two variables, foo and baz. If you get the foo value early on in the chain, but the baz value later, it can be annoying to wait until you have both variables in the same place to pass them to the prompt template. Instead, you can partial the prompt template with the foo value, and then pass the partialed prompt template along and just use that. Below is an example of doing this:
from langchain.prompts import PromptTemplate
prompt = PromptTemplate(template="{foo}{bar}", input_variables=["foo", "bar"])
partial_prompt = prompt.partial(foo="foo");
print(partial_prompt.format(bar="baz"))
foobaz
You can also just initialize the prompt with the partialed variables.
prompt = PromptTemplate(template="{foo}{bar}", input_variables=["bar"], partial_variables={"foo": "foo"})
print(prompt.format(bar="baz"))
foobaz


print(prompt.format(bar="baz"))
foobaz
Partial With Functions#
The other common use is to partial with a function. The use case for this is when you have a variable you know that you always want to fetch in a common way. A prime example of this is with date or time. Imagine you have a prompt which you always want to have the current date. You can’t hard code it in the prompt, and passing it along with the other input variables is a bit annoying. In this case, it’s very handy to be able to partial the prompt with a function that always returns the current date.
from datetime import datetime
def _get_datetime():
    now = datetime.now()
    return now.strftime("%m/%d/%Y, %H:%M:%S")
prompt = PromptTemplate(
    template="Tell me a {adjective} joke about the day {date}",
    input_variables=["adjective", "date"]
);
partial_prompt = prompt.partial(date=_get_datetime)
print(partial_prompt.format(adjective="funny"))
Tell me a funny joke about the day 02/27/2023, 22:15:16
You can also just initialize the prompt with the partialed variables, which often makes more sense in this workflow.
prompt = PromptTemplate(
    template="Tell me a {adjective} joke about the day {date}",
    input_variables=["adjective"],
    partial_variables={"date": _get_datetime}
);
print(prompt.format(adjective="funny"))
Tell me a funny joke about the day 02/27/2023, 22:15:16
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Partial With Strings
Partial With Functions
By Harrison Chase


Contents

Partial With Strings
Partial With Functions
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


.ipynb
.pdf
How to create a custom prompt template
 Contents
Why are custom prompt templates needed?
Creating a Custom Prompt Template
Use the custom prompt template
How to create a custom prompt template#
Let’s suppose we want the LLM to generate English language explanations of a function given its name. To achieve this task, we will create a custom prompt template that takes in the function name as input, and formats the prompt template to provide the source code of the function.
Why are custom prompt templates needed?#
LangChain provides a set of default prompt templates that can be used to generate prompts for a variety of tasks. However, there may be cases where the default prompt templates do not meet your needs. For example, you may want to create a prompt template with specific dynamic instructions for your language model. In such cases, you can create a custom prompt template.
Take a look at the current set of default prompt templates here.
Creating a Custom Prompt Template#
There are essentially two distinct prompt templates available - string prompt templates and chat prompt templates. String prompt templates provides a simple prompt in string format, while chat prompt templates produces a more structured prompt to be used with a chat API.
In this guide, we will create a custom prompt using a string prompt template.
To create a custom string prompt template, there are two requirements:
It has an input_variables attribute that exposes what input variables the prompt template expects.
It exposes a format method that takes in keyword arguments corresponding to the expected input_variables and returns the formatted prompt.
We will create a custom prompt template that takes in the function name as input and formats the prompt to provide the source code of the function. To achieve this, let’s first create a function that will return the source code of a function given its name.
import inspect
def get_source_code(function_name):
    # Get the source code of the function


import inspect
def get_source_code(function_name):
    # Get the source code of the function
    return inspect.getsource(function_name)
Next, we’ll create a custom prompt template that takes in the function name as input, and formats the prompt template to provide the source code of the function.
from langchain.prompts import StringPromptTemplate
from pydantic import BaseModel, validator
class FunctionExplainerPromptTemplate(StringPromptTemplate, BaseModel):
    """ A custom prompt template that takes in the function name as input, and formats the prompt template to provide the source code of the function. """
    @validator("input_variables")
    def validate_input_variables(cls, v):
        """ Validate that the input variables are correct. """
        if len(v) != 1 or "function_name" not in v:
            raise ValueError("function_name must be the only input_variable.")
        return v
    def format(self, **kwargs) -> str:
        # Get the source code of the function
        source_code = get_source_code(kwargs["function_name"])
        # Generate the prompt to be sent to the language model
        prompt = f"""
        Given the function name and source code, generate an English language explanation of the function.
        Function Name: {kwargs["function_name"].__name__}
        Source Code:
        {source_code}
        Explanation:
        """
        return prompt

    def _prompt_type(self):
        return "function-explainer"
Use the custom prompt template#
Now that we have created a custom prompt template, we can use it to generate prompts for our task.
fn_explainer = FunctionExplainerPromptTemplate(input_variables=["function_name"])
# Generate a prompt for the function "get_source_code"
prompt = fn_explainer.format(function_name=get_source_code)
print(prompt)


prompt = fn_explainer.format(function_name=get_source_code)
print(prompt)
        Given the function name and source code, generate an English language explanation of the function.
        Function Name: get_source_code
        Source Code:
        def get_source_code(function_name):
    # Get the source code of the function
    return inspect.getsource(function_name)
        Explanation:

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Why are custom prompt templates needed?
Creating a Custom Prompt Template
Use the custom prompt template
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


.ipynb
.pdf
How to create a prompt template that uses few shot examples
 Contents
Use Case
Using an example set
Create the example set
Create a formatter for the few shot examples
Feed examples and formatter to FewShotPromptTemplate
Using an example selector
Feed examples into ExampleSelector
Feed example selector into FewShotPromptTemplate
How to create a prompt template that uses few shot examples#
In this tutorial, we’ll learn how to create a prompt template that uses few shot examples.
We’ll use the FewShotPromptTemplate class to create a prompt template that uses few shot examples. This class either takes in a set of examples, or an ExampleSelector object. In this tutorial, we’ll go over both options.
Use Case#
In this tutorial, we’ll configure few shot examples for self-ask with search.
Using an example set#
Create the example set#
To get started, create a list of few shot examples. Each example should be a dictionary with the keys being the input variables and the values being the values for those input variables.
from langchain.prompts.few_shot import FewShotPromptTemplate
from langchain.prompts.prompt import PromptTemplate
examples = [
  {
    "question": "Who lived longer, Muhammad Ali or Alan Turing?",
    "answer":
"""
Are follow up questions needed here: Yes.
Follow up: How old was Muhammad Ali when he died?
Intermediate answer: Muhammad Ali was 74 years old when he died.
Follow up: How old was Alan Turing when he died?
Intermediate answer: Alan Turing was 41 years old when he died.
So the final answer is: Muhammad Ali
"""
  },
  {
    "question": "When was the founder of craigslist born?",
    "answer":
"""
Are follow up questions needed here: Yes.


"answer":
"""
Are follow up questions needed here: Yes.
Follow up: Who was the founder of craigslist?
Intermediate answer: Craigslist was founded by Craig Newmark.
Follow up: When was Craig Newmark born?
Intermediate answer: Craig Newmark was born on December 6, 1952.
So the final answer is: December 6, 1952
"""
  },
  {
    "question": "Who was the maternal grandfather of George Washington?",
    "answer":
"""
Are follow up questions needed here: Yes.
Follow up: Who was the mother of George Washington?
Intermediate answer: The mother of George Washington was Mary Ball Washington.
Follow up: Who was the father of Mary Ball Washington?
Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
So the final answer is: Joseph Ball
"""
  },
  {
    "question": "Are both the directors of Jaws and Casino Royale from the same country?",
    "answer":
"""
Are follow up questions needed here: Yes.
Follow up: Who is the director of Jaws?
Intermediate Answer: The director of Jaws is Steven Spielberg.
Follow up: Where is Steven Spielberg from?
Intermediate Answer: The United States.
Follow up: Who is the director of Casino Royale?
Intermediate Answer: The director of Casino Royale is Martin Campbell.
Follow up: Where is Martin Campbell from?
Intermediate Answer: New Zealand.
So the final answer is: No
"""
  }
]
Create a formatter for the few shot examples#
Configure a formatter that will format the few shot examples into a string. This formatter should be a PromptTemplate object.
example_prompt = PromptTemplate(input_variables=["question", "answer"], template="Question: {question}\n{answer}")


print(example_prompt.format(**examples[0]))
Question: Who lived longer, Muhammad Ali or Alan Turing?
Are follow up questions needed here: Yes.
Follow up: How old was Muhammad Ali when he died?
Intermediate answer: Muhammad Ali was 74 years old when he died.
Follow up: How old was Alan Turing when he died?
Intermediate answer: Alan Turing was 41 years old when he died.
So the final answer is: Muhammad Ali
Feed examples and formatter to FewShotPromptTemplate#
Finally, create a FewShotPromptTemplate object. This object takes in the few shot examples and the formatter for the few shot examples.
prompt = FewShotPromptTemplate(
    examples=examples,
    example_prompt=example_prompt,
    suffix="Question: {input}",
    input_variables=["input"]
)
print(prompt.format(input="Who was the father of Mary Ball Washington?"))
Question: Who lived longer, Muhammad Ali or Alan Turing?
Are follow up questions needed here: Yes.
Follow up: How old was Muhammad Ali when he died?
Intermediate answer: Muhammad Ali was 74 years old when he died.
Follow up: How old was Alan Turing when he died?
Intermediate answer: Alan Turing was 41 years old when he died.
So the final answer is: Muhammad Ali
Question: When was the founder of craigslist born?
Are follow up questions needed here: Yes.
Follow up: Who was the founder of craigslist?
Intermediate answer: Craigslist was founded by Craig Newmark.
Follow up: When was Craig Newmark born?
Intermediate answer: Craig Newmark was born on December 6, 1952.
So the final answer is: December 6, 1952
Question: Who was the maternal grandfather of George Washington?
Are follow up questions needed here: Yes.


Are follow up questions needed here: Yes.
Follow up: Who was the mother of George Washington?
Intermediate answer: The mother of George Washington was Mary Ball Washington.
Follow up: Who was the father of Mary Ball Washington?
Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
So the final answer is: Joseph Ball
Question: Are both the directors of Jaws and Casino Royale from the same country?
Are follow up questions needed here: Yes.
Follow up: Who is the director of Jaws?
Intermediate Answer: The director of Jaws is Steven Spielberg.
Follow up: Where is Steven Spielberg from?
Intermediate Answer: The United States.
Follow up: Who is the director of Casino Royale?
Intermediate Answer: The director of Casino Royale is Martin Campbell.
Follow up: Where is Martin Campbell from?
Intermediate Answer: New Zealand.
So the final answer is: No
Question: Who was the father of Mary Ball Washington?
Using an example selector#
Feed examples into ExampleSelector#
We will reuse the example set and the formatter from the previous section. However, instead of feeding the examples directly into the FewShotPromptTemplate object, we will feed them into an ExampleSelector object.
In this tutorial, we will use the SemanticSimilarityExampleSelector class. This class selects few shot examples based on their similarity to the input. It uses an embedding model to compute the similarity between the input and the few shot examples, as well as a vector store to perform the nearest neighbor search.
from langchain.prompts.example_selector import SemanticSimilarityExampleSelector
from langchain.vectorstores import Chroma
from langchain.embeddings import OpenAIEmbeddings
example_selector = SemanticSimilarityExampleSelector.from_examples(
    # This is the list of examples available to select from.
    examples,


# This is the list of examples available to select from.
    examples,
    # This is the embedding class used to produce embeddings which are used to measure semantic similarity.
    OpenAIEmbeddings(),
    # This is the VectorStore class that is used to store the embeddings and do a similarity search over.
    Chroma,
    # This is the number of examples to produce.
    k=1
)
# Select the most similar example to the input.
question = "Who was the father of Mary Ball Washington?"
selected_examples = example_selector.select_examples({"question": question})
print(f"Examples most similar to the input: {question}")
for example in selected_examples:
    print("\n")
    for k, v in example.items():
        print(f"{k}: {v}")
Running Chroma using direct local API.
Using DuckDB in-memory for database. Data will be transient.
Examples most similar to the input: Who was the father of Mary Ball Washington?
question: Who was the maternal grandfather of George Washington?
answer:
Are follow up questions needed here: Yes.
Follow up: Who was the mother of George Washington?
Intermediate answer: The mother of George Washington was Mary Ball Washington.
Follow up: Who was the father of Mary Ball Washington?
Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
So the final answer is: Joseph Ball
Feed example selector into FewShotPromptTemplate#
Finally, create a FewShotPromptTemplate object. This object takes in the example selector and the formatter for the few shot examples.
prompt = FewShotPromptTemplate(
    example_selector=example_selector,
    example_prompt=example_prompt,
    suffix="Question: {input}",
    input_variables=["input"]
)


suffix="Question: {input}",
    input_variables=["input"]
)
print(prompt.format(input="Who was the father of Mary Ball Washington?"))
Question: Who was the maternal grandfather of George Washington?
Are follow up questions needed here: Yes.
Follow up: Who was the mother of George Washington?
Intermediate answer: The mother of George Washington was Mary Ball Washington.
Follow up: Who was the father of Mary Ball Washington?
Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
So the final answer is: Joseph Ball
Question: Who was the father of Mary Ball Washington?
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How to create a custom prompt template
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How to work with partial Prompt Templates
 Contents

Use Case
Using an example set
Create the example set
Create a formatter for the few shot examples
Feed examples and formatter to FewShotPromptTemplate
Using an example selector
Feed examples into ExampleSelector
Feed example selector into FewShotPromptTemplate
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


.ipynb
.pdf
How to serialize prompts
 Contents
PromptTemplate
Loading from YAML
Loading from JSON
Loading Template from a File
FewShotPromptTemplate
Examples
Loading from YAML
Loading from JSON
Examples in the Config
Example Prompt from a File
How to serialize prompts#
It is often preferrable to store prompts not as python code but as files. This can make it easy to share, store, and version prompts. This notebook covers how to do that in LangChain, walking through all the different types of prompts and the different serialization options.
At a high level, the following design principles are applied to serialization:
Both JSON and YAML are supported. We want to support serialization methods that are human readable on disk, and YAML and JSON are two of the most popular methods for that. Note that this rule applies to prompts. For other assets, like Examples, different serialization methods may be supported.
We support specifying everything in one file, or storing different components (templates, examples, etc) in different files and referencing them. For some cases, storing everything in file makes the most sense, but for others it is preferrable to split up some of the assets (long templates, large examples, reusable components). LangChain supports both.
There is also a single entry point to load prompts from disk, making it easy to load any type of prompt.
# All prompts are loaded through the `load_prompt` function.
from langchain.prompts import load_prompt
PromptTemplate#
This section covers examples for loading a PromptTemplate.
Loading from YAML#
This shows an example of loading a PromptTemplate from YAML.
!cat simple_prompt.yaml
_type: prompt
input_variables:
    ["adjective", "content"]
template:
    Tell me a {adjective} joke about {content}.
prompt = load_prompt("simple_prompt.yaml")


prompt = load_prompt("simple_prompt.yaml")
print(prompt.format(adjective="funny", content="chickens"))
Tell me a funny joke about chickens.
Loading from JSON#
This shows an example of loading a PromptTemplate from JSON.
!cat simple_prompt.json
{
    "_type": "prompt",
    "input_variables": ["adjective", "content"],
    "template": "Tell me a {adjective} joke about {content}."
}
prompt = load_prompt("simple_prompt.json")
print(prompt.format(adjective="funny", content="chickens"))
Tell me a funny joke about chickens.
Loading Template from a File#
This shows an example of storing the template in a separate file and then referencing it in the config. Notice that the key changes from template to template_path.
!cat simple_template.txt
Tell me a {adjective} joke about {content}.
!cat simple_prompt_with_template_file.json
{
    "_type": "prompt",
    "input_variables": ["adjective", "content"],
    "template_path": "simple_template.txt"
}
prompt = load_prompt("simple_prompt_with_template_file.json")
print(prompt.format(adjective="funny", content="chickens"))
Tell me a funny joke about chickens.
FewShotPromptTemplate#
This section covers examples for loading few shot prompt templates.
Examples#
This shows an example of what examples stored as json might look like.
!cat examples.json
[
    {"input": "happy", "output": "sad"},
    {"input": "tall", "output": "short"}
]
And here is what the same examples stored as yaml might look like.
!cat examples.yaml
- input: happy
  output: sad
- input: tall
  output: short
Loading from YAML#


output: sad
- input: tall
  output: short
Loading from YAML#
This shows an example of loading a few shot example from YAML.
!cat few_shot_prompt.yaml
_type: few_shot
input_variables:
    ["adjective"]
prefix:
    Write antonyms for the following words.
example_prompt:
    _type: prompt
    input_variables:
        ["input", "output"]
    template:
        "Input: {input}\nOutput: {output}"
examples:
    examples.json
suffix:
    "Input: {adjective}\nOutput:"
prompt = load_prompt("few_shot_prompt.yaml")
print(prompt.format(adjective="funny"))
Write antonyms for the following words.
Input: happy
Output: sad
Input: tall
Output: short
Input: funny
Output:
The same would work if you loaded examples from the yaml file.
!cat few_shot_prompt_yaml_examples.yaml
_type: few_shot
input_variables:
    ["adjective"]
prefix:
    Write antonyms for the following words.
example_prompt:
    _type: prompt
    input_variables:
        ["input", "output"]
    template:
        "Input: {input}\nOutput: {output}"
examples:
    examples.yaml
suffix:
    "Input: {adjective}\nOutput:"
prompt = load_prompt("few_shot_prompt_yaml_examples.yaml")
print(prompt.format(adjective="funny"))
Write antonyms for the following words.
Input: happy
Output: sad
Input: tall
Output: short
Input: funny
Output:
Loading from JSON#
This shows an example of loading a few shot example from JSON.
!cat few_shot_prompt.json
{
    "_type": "few_shot",


!cat few_shot_prompt.json
{
    "_type": "few_shot",
    "input_variables": ["adjective"],
    "prefix": "Write antonyms for the following words.",
    "example_prompt": {
        "_type": "prompt",
        "input_variables": ["input", "output"],
        "template": "Input: {input}\nOutput: {output}"
    },
    "examples": "examples.json",
    "suffix": "Input: {adjective}\nOutput:"
}
prompt = load_prompt("few_shot_prompt.json")
print(prompt.format(adjective="funny"))
Write antonyms for the following words.
Input: happy
Output: sad
Input: tall
Output: short
Input: funny
Output:
Examples in the Config#
This shows an example of referencing the examples directly in the config.
!cat few_shot_prompt_examples_in.json
{
    "_type": "few_shot",
    "input_variables": ["adjective"],
    "prefix": "Write antonyms for the following words.",
    "example_prompt": {
        "_type": "prompt",
        "input_variables": ["input", "output"],
        "template": "Input: {input}\nOutput: {output}"
    },
    "examples": [
        {"input": "happy", "output": "sad"},
        {"input": "tall", "output": "short"}
    ],
    "suffix": "Input: {adjective}\nOutput:"
}
prompt = load_prompt("few_shot_prompt_examples_in.json")
print(prompt.format(adjective="funny"))
Write antonyms for the following words.
Input: happy
Output: sad
Input: tall
Output: short
Input: funny
Output:
Example Prompt from a File#


Output: short
Input: funny
Output:
Example Prompt from a File#
This shows an example of loading the PromptTemplate that is used to format the examples from a separate file. Note that the key changes from example_prompt to example_prompt_path.
!cat example_prompt.json
{
    "_type": "prompt",
    "input_variables": ["input", "output"],
    "template": "Input: {input}\nOutput: {output}"
}
!cat few_shot_prompt_example_prompt.json
{
    "_type": "few_shot",
    "input_variables": ["adjective"],
    "prefix": "Write antonyms for the following words.",
    "example_prompt_path": "example_prompt.json",
    "examples": "examples.json",
    "suffix": "Input: {adjective}\nOutput:"
}
prompt = load_prompt("few_shot_prompt_example_prompt.json")
print(prompt.format(adjective="funny"))
Write antonyms for the following words.
Input: happy
Output: sad
Input: tall
Output: short
Input: funny
Output:
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Prompts
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PromptTemplate
Loading from YAML
Loading from JSON
Loading Template from a File
FewShotPromptTemplate
Examples
Loading from YAML
Loading from JSON
Examples in the Config
Example Prompt from a File
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


.ipynb
.pdf
Output Parsers
Output Parsers#
Language models output text. But many times you may want to get more structured information than just text back. This is where output parsers come in.
Output parsers are classes that help structure language model responses. There are two main methods an output parser must implement:
get_format_instructions() -> str: A method which returns a string containing instructions for how the output of a language model should be formatted.
parse(str) -> Any: A method which takes in a string (assumed to be the response from a language model) and parses it into some structure.
And then one optional one:
parse_with_prompt(str, PromptValue) -> Any: A method which takes in a string (assumed to be the response from a language model) and a prompt (assumed to the prompt that generated such a response) and parses it into some structure. The prompt is largely provided in the event the OutputParser wants to retry or fix the output in some way, and needs information from the prompt to do so.
Below we go over the main type of output parser, the PydanticOutputParser. See the examples folder for other options.
from langchain.prompts import PromptTemplate, ChatPromptTemplate, HumanMessagePromptTemplate
from langchain.llms import OpenAI
from langchain.chat_models import ChatOpenAI
from langchain.output_parsers import PydanticOutputParser
from pydantic import BaseModel, Field, validator
from typing import List
model_name = 'text-davinci-003'
temperature = 0.0
model = OpenAI(model_name=model_name, temperature=temperature)
# Define your desired data structure.
class Joke(BaseModel):
    setup: str = Field(description="question to set up a joke")
    punchline: str = Field(description="answer to resolve the joke")


punchline: str = Field(description="answer to resolve the joke")

    # You can add custom validation logic easily with Pydantic.
    @validator('setup')
    def question_ends_with_question_mark(cls, field):
        if field[-1] != '?':
            raise ValueError("Badly formed question!")
        return field
# Set up a parser + inject instructions into the prompt template.
parser = PydanticOutputParser(pydantic_object=Joke)
prompt = PromptTemplate(
    template="Answer the user query.\n{format_instructions}\n{query}\n",
    input_variables=["query"],
    partial_variables={"format_instructions": parser.get_format_instructions()}
)
# And a query intented to prompt a language model to populate the data structure.
joke_query = "Tell me a joke."
_input = prompt.format_prompt(query=joke_query)
output = model(_input.to_string())
parser.parse(output)
Joke(setup='Why did the chicken cross the road?', punchline='To get to the other side!')
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CommaSeparatedListOutputParser
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  Last updated on Apr 21, 2023.


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OutputFixingParser
OutputFixingParser#
This output parser wraps another output parser and tries to fix any mmistakes
The Pydantic guardrail simply tries to parse the LLM response. If it does not parse correctly, then it errors.
But we can do other things besides throw errors. Specifically, we can pass the misformatted output, along with the formatted instructions, to the model and ask it to fix it.
For this example, we’ll use the above OutputParser. Here’s what happens if we pass it a result that does not comply with the schema:
from langchain.prompts import PromptTemplate, ChatPromptTemplate, HumanMessagePromptTemplate
from langchain.llms import OpenAI
from langchain.chat_models import ChatOpenAI
from langchain.output_parsers import PydanticOutputParser
from pydantic import BaseModel, Field, validator
from typing import List
class Actor(BaseModel):
    name: str = Field(description="name of an actor")
    film_names: List[str] = Field(description="list of names of films they starred in")

actor_query = "Generate the filmography for a random actor."
parser = PydanticOutputParser(pydantic_object=Actor)
misformatted = "{'name': 'Tom Hanks', 'film_names': ['Forrest Gump']}"
parser.parse(misformatted)
---------------------------------------------------------------------------
JSONDecodeError                           Traceback (most recent call last)
File ~/workplace/langchain/langchain/output_parsers/pydantic.py:23, in PydanticOutputParser.parse(self, text)
     22     json_str = match.group()
---> 23 json_object = json.loads(json_str)
     24 return self.pydantic_object.parse_obj(json_object)


24 return self.pydantic_object.parse_obj(json_object)
File ~/.pyenv/versions/3.9.1/lib/python3.9/json/__init__.py:346, in loads(s, cls, object_hook, parse_float, parse_int, parse_constant, object_pairs_hook, **kw)
    343 if (cls is None and object_hook is None and
    344         parse_int is None and parse_float is None and
    345         parse_constant is None and object_pairs_hook is None and not kw):
--> 346     return _default_decoder.decode(s)
    347 if cls is None:
File ~/.pyenv/versions/3.9.1/lib/python3.9/json/decoder.py:337, in JSONDecoder.decode(self, s, _w)
    333 """Return the Python representation of ``s`` (a ``str`` instance
    334 containing a JSON document).
    335
    336 """
--> 337 obj, end = self.raw_decode(s, idx=_w(s, 0).end())
    338 end = _w(s, end).end()
File ~/.pyenv/versions/3.9.1/lib/python3.9/json/decoder.py:353, in JSONDecoder.raw_decode(self, s, idx)
    352 try:
--> 353     obj, end = self.scan_once(s, idx)
    354 except StopIteration as err:
JSONDecodeError: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)
During handling of the above exception, another exception occurred:
OutputParserException                     Traceback (most recent call last)
Cell In[6], line 1
----> 1 parser.parse(misformatted)


Cell In[6], line 1
----> 1 parser.parse(misformatted)
File ~/workplace/langchain/langchain/output_parsers/pydantic.py:29, in PydanticOutputParser.parse(self, text)
     27 name = self.pydantic_object.__name__
     28 msg = f"Failed to parse {name} from completion {text}. Got: {e}"
---> 29 raise OutputParserException(msg)
OutputParserException: Failed to parse Actor from completion {'name': 'Tom Hanks', 'film_names': ['Forrest Gump']}. Got: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)
Now we can construct and use a OutputFixingParser. This output parser takes as an argument another output parser but also an LLM with which to try to correct any formatting mistakes.
from langchain.output_parsers import OutputFixingParser
new_parser = OutputFixingParser.from_llm(parser=parser, llm=ChatOpenAI())
new_parser.parse(misformatted)
Actor(name='Tom Hanks', film_names=['Forrest Gump'])
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PydanticOutputParser
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  Last updated on Apr 21, 2023.


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RetryOutputParser
RetryOutputParser#
While in some cases it is possible to fix any parsing mistakes by only looking at the output, in other cases it can’t. An example of this is when the output is not just in the incorrect format, but is partially complete. Consider the below example.
from langchain.prompts import PromptTemplate, ChatPromptTemplate, HumanMessagePromptTemplate
from langchain.llms import OpenAI
from langchain.chat_models import ChatOpenAI
from langchain.output_parsers import PydanticOutputParser, OutputFixingParser, RetryOutputParser
from pydantic import BaseModel, Field, validator
from typing import List
template = """Based on the user question, provide an Action and Action Input for what step should be taken.
{format_instructions}
Question: {query}
Response:"""
class Action(BaseModel):
    action: str = Field(description="action to take")
    action_input: str = Field(description="input to the action")

parser = PydanticOutputParser(pydantic_object=Action)
prompt = PromptTemplate(
    template="Answer the user query.\n{format_instructions}\n{query}\n",
    input_variables=["query"],
    partial_variables={"format_instructions": parser.get_format_instructions()}
)
prompt_value = prompt.format_prompt(query="who is leo di caprios gf?")
bad_response = '{"action": "search"}'
If we try to parse this response as is, we will get an error
parser.parse(bad_response)
---------------------------------------------------------------------------
ValidationError                           Traceback (most recent call last)
File ~/workplace/langchain/langchain/output_parsers/pydantic.py:24, in PydanticOutputParser.parse(self, text)
     23     json_object = json.loads(json_str)


23     json_object = json.loads(json_str)
---> 24     return self.pydantic_object.parse_obj(json_object)
     26 except (json.JSONDecodeError, ValidationError) as e:
File ~/.pyenv/versions/3.9.1/envs/langchain/lib/python3.9/site-packages/pydantic/main.py:527, in pydantic.main.BaseModel.parse_obj()
File ~/.pyenv/versions/3.9.1/envs/langchain/lib/python3.9/site-packages/pydantic/main.py:342, in pydantic.main.BaseModel.__init__()
ValidationError: 1 validation error for Action
action_input
  field required (type=value_error.missing)
During handling of the above exception, another exception occurred:
OutputParserException                     Traceback (most recent call last)
Cell In[6], line 1
----> 1 parser.parse(bad_response)
File ~/workplace/langchain/langchain/output_parsers/pydantic.py:29, in PydanticOutputParser.parse(self, text)
     27 name = self.pydantic_object.__name__
     28 msg = f"Failed to parse {name} from completion {text}. Got: {e}"
---> 29 raise OutputParserException(msg)
OutputParserException: Failed to parse Action from completion {"action": "search"}. Got: 1 validation error for Action
action_input
  field required (type=value_error.missing)
If we try to use the OutputFixingParser to fix this error, it will be confused - namely, it doesn’t know what to actually put for action input.
fix_parser = OutputFixingParser.from_llm(parser=parser, llm=ChatOpenAI())
fix_parser.parse(bad_response)
Action(action='search', action_input='')


fix_parser.parse(bad_response)
Action(action='search', action_input='')
Instead, we can use the RetryOutputParser, which passes in the prompt (as well as the original output) to try again to get a better response.
from langchain.output_parsers import RetryWithErrorOutputParser
retry_parser = RetryWithErrorOutputParser.from_llm(parser=parser, llm=OpenAI(temperature=0))
retry_parser.parse_with_prompt(bad_response, prompt_value)
Action(action='search', action_input='who is leo di caprios gf?')
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PydanticOutputParser
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Structured Output Parser
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


.ipynb
.pdf
PydanticOutputParser
PydanticOutputParser#
This output parser allows users to specify an arbitrary JSON schema and query LLMs for JSON outputs that conform to that schema.
Keep in mind that large language models are leaky abstractions! You’ll have to use an LLM with sufficient capacity to generate well-formed JSON. In the OpenAI family, DaVinci can do reliably but Curie’s ability already drops off dramatically.
Use Pydantic to declare your data model. Pydantic’s BaseModel like a Python dataclass, but with actual type checking + coercion.
from langchain.prompts import PromptTemplate, ChatPromptTemplate, HumanMessagePromptTemplate
from langchain.llms import OpenAI
from langchain.chat_models import ChatOpenAI
from langchain.output_parsers import PydanticOutputParser
from pydantic import BaseModel, Field, validator
from typing import List
model_name = 'text-davinci-003'
temperature = 0.0
model = OpenAI(model_name=model_name, temperature=temperature)
# Define your desired data structure.
class Joke(BaseModel):
    setup: str = Field(description="question to set up a joke")
    punchline: str = Field(description="answer to resolve the joke")

    # You can add custom validation logic easily with Pydantic.
    @validator('setup')
    def question_ends_with_question_mark(cls, field):
        if field[-1] != '?':
            raise ValueError("Badly formed question!")
        return field
# And a query intented to prompt a language model to populate the data structure.
joke_query = "Tell me a joke."
# Set up a parser + inject instructions into the prompt template.
parser = PydanticOutputParser(pydantic_object=Joke)
prompt = PromptTemplate(


prompt = PromptTemplate(
    template="Answer the user query.\n{format_instructions}\n{query}\n",
    input_variables=["query"],
    partial_variables={"format_instructions": parser.get_format_instructions()}
)
_input = prompt.format_prompt(query=joke_query)
output = model(_input.to_string())
parser.parse(output)
Joke(setup='Why did the chicken cross the road?', punchline='To get to the other side!')
# Here's another example, but with a compound typed field.
class Actor(BaseModel):
    name: str = Field(description="name of an actor")
    film_names: List[str] = Field(description="list of names of films they starred in")

actor_query = "Generate the filmography for a random actor."
parser = PydanticOutputParser(pydantic_object=Actor)
prompt = PromptTemplate(
    template="Answer the user query.\n{format_instructions}\n{query}\n",
    input_variables=["query"],
    partial_variables={"format_instructions": parser.get_format_instructions()}
)
_input = prompt.format_prompt(query=actor_query)
output = model(_input.to_string())
parser.parse(output)
Actor(name='Tom Hanks', film_names=['Forrest Gump', 'Saving Private Ryan', 'The Green Mile', 'Cast Away', 'Toy Story'])
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OutputFixingParser
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RetryOutputParser
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


.ipynb
.pdf
CommaSeparatedListOutputParser
CommaSeparatedListOutputParser#
Here’s another parser strictly less powerful than Pydantic/JSON parsing.
from langchain.output_parsers import CommaSeparatedListOutputParser
from langchain.prompts import PromptTemplate, ChatPromptTemplate, HumanMessagePromptTemplate
from langchain.llms import OpenAI
from langchain.chat_models import ChatOpenAI
output_parser = CommaSeparatedListOutputParser()
format_instructions = output_parser.get_format_instructions()
prompt = PromptTemplate(
    template="List five {subject}.\n{format_instructions}",
    input_variables=["subject"],
    partial_variables={"format_instructions": format_instructions}
)
model = OpenAI(temperature=0)
_input = prompt.format(subject="ice cream flavors")
output = model(_input)
output_parser.parse(output)
['Vanilla',
 'Chocolate',
 'Strawberry',
 'Mint Chocolate Chip',
 'Cookies and Cream']
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Output Parsers
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OutputFixingParser
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


.ipynb
.pdf
Structured Output Parser
Structured Output Parser#
While the Pydantic/JSON parser is more powerful, we initially experimented data structures having text fields only.
from langchain.output_parsers import StructuredOutputParser, ResponseSchema
from langchain.prompts import PromptTemplate, ChatPromptTemplate, HumanMessagePromptTemplate
from langchain.llms import OpenAI
from langchain.chat_models import ChatOpenAI
Here we define the response schema we want to receive.
response_schemas = [
    ResponseSchema(name="answer", description="answer to the user's question"),
    ResponseSchema(name="source", description="source used to answer the user's question, should be a website.")
]
output_parser = StructuredOutputParser.from_response_schemas(response_schemas)
We now get a string that contains instructions for how the response should be formatted, and we then insert that into our prompt.
format_instructions = output_parser.get_format_instructions()
prompt = PromptTemplate(
    template="answer the users question as best as possible.\n{format_instructions}\n{question}",
    input_variables=["question"],
    partial_variables={"format_instructions": format_instructions}
)
We can now use this to format a prompt to send to the language model, and then parse the returned result.
model = OpenAI(temperature=0)
_input = prompt.format_prompt(question="what's the capital of france")
output = model(_input.to_string())
output_parser.parse(output)
{'answer': 'Paris', 'source': 'https://en.wikipedia.org/wiki/Paris'}
And here’s an example of using this in a chat model
chat_model = ChatOpenAI(temperature=0)
prompt = ChatPromptTemplate(
    messages=[
        HumanMessagePromptTemplate.from_template("answer the users question as best as possible.\n{format_instructions}\n{question}")


],
    input_variables=["question"],
    partial_variables={"format_instructions": format_instructions}
)
_input = prompt.format_prompt(question="what's the capital of france")
output = chat_model(_input.to_messages())
output_parser.parse(output.content)
{'answer': 'Paris', 'source': 'https://en.wikipedia.org/wiki/Paris'}
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RetryOutputParser
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Indexes
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Apr 21, 2023.


.ipynb
.pdf
LengthBased ExampleSelector
LengthBased ExampleSelector#
This ExampleSelector selects which examples to use based on length. This is useful when you are worried about constructing a prompt that will go over the length of the context window. For longer inputs, it will select fewer examples to include, while for shorter inputs it will select more.
from langchain.prompts import PromptTemplate
from langchain.prompts import FewShotPromptTemplate
from langchain.prompts.example_selector import LengthBasedExampleSelector
# These are a lot of examples of a pretend task of creating antonyms.
examples = [
    {"input": "happy", "output": "sad"},
    {"input": "tall", "output": "short"},
    {"input": "energetic", "output": "lethargic"},
    {"input": "sunny", "output": "gloomy"},
    {"input": "windy", "output": "calm"},
]
example_prompt = PromptTemplate(
    input_variables=["input", "output"],
    template="Input: {input}\nOutput: {output}",
)
example_selector = LengthBasedExampleSelector(
    # These are the examples it has available to choose from.
    examples=examples,
    # This is the PromptTemplate being used to format the examples.
    example_prompt=example_prompt,
    # This is the maximum length that the formatted examples should be.
    # Length is measured by the get_text_length function below.
    max_length=25,
    # This is the function used to get the length of a string, which is used
    # to determine which examples to include. It is commented out because
    # it is provided as a default value if none is specified.