langchain.js
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    Class LengthBasedExampleSelector

    A specialized example selector that selects examples based on their length, ensuring that the total length of the selected examples does not exceed a specified maximum length.

    const exampleSelector = new LengthBasedExampleSelector(
      [
        { input: "happy", output: "sad" },
        { input: "tall", output: "short" },
        { input: "energetic", output: "lethargic" },
        { input: "sunny", output: "gloomy" },
        { input: "windy", output: "calm" },
      ],
      {
        examplePrompt: new PromptTemplate({
          inputVariables: ["input", "output"],
          template: "Input: {input}\nOutput: {output}",
        }),
        maxLength: 25,
      },
    );
    const dynamicPrompt = new FewShotPromptTemplate({
      exampleSelector,
      examplePrompt: new PromptTemplate({
        inputVariables: ["input", "output"],
        template: "Input: {input}\nOutput: {output}",
      }),
      prefix: "Give the antonym of every input",
      suffix: "Input: {adjective}\nOutput:",
      inputVariables: ["adjective"],
    });
    console.log(dynamicPrompt.format({ adjective: "big" }));
    console.log(
      dynamicPrompt.format({
        adjective:
          "big and huge and massive and large and gigantic and tall and much much much much much bigger than everything else",
      }),
    );

    Hierarchy (View Summary)

    Index

    Constructors

    constructor

    Properties

    examplePrompt examples exampleTextLengths getTextLength lc_kwargs lc_namespace lc_serializable maxLength

    Accessors

    lc_aliases lc_attributes lc_id lc_secrets lc_serializable_keys

    Methods

    addExample calculateExampleTextLengths selectExamples toJSON toJSONNotImplemented fromExamples lc_name

    Constructors

    Properties

    examplePrompt: PromptTemplate
    examples: Example[] = []
    exampleTextLengths: number[] = []
    getTextLength: (text: string) => number = getLengthBased
    lc_kwargs: SerializedFields
    lc_namespace: string[] = ...

    A path to the module that contains the class, eg. ["langchain", "llms"] Usually should be the same as the entrypoint the class is exported from.

    lc_serializable: boolean = false
    maxLength: number = 2048

    Accessors

    • get lc_aliases(): undefined | { [key: string]: string }

      A map of aliases for constructor args. Keys are the attribute names, e.g. "foo". Values are the alias that will replace the key in serialization. This is used to eg. make argument names match Python.

      Returns undefined | { [key: string]: string }

    • get lc_attributes(): undefined | SerializedFields

      A map of additional attributes to merge with constructor args. Keys are the attribute names, e.g. "foo". Values are the attribute values, which will be serialized. These attributes need to be accepted by the constructor as arguments.

      Returns undefined | SerializedFields

    • get lc_id(): string[]

      The final serialized identifier for the module.

      Returns string[]

    • get lc_secrets(): undefined | { [key: string]: string }

      A map of secrets, which will be omitted from serialization. Keys are paths to the secret in constructor args, e.g. "foo.bar.baz". Values are the secret ids, which will be used when deserializing.

      Returns undefined | { [key: string]: string }

    • get lc_serializable_keys(): undefined | string[]

      A manual list of keys that should be serialized. If not overridden, all fields passed into the constructor will be serialized.

      Returns undefined | string[]

    Methods

    • Adds an example to the list of examples and calculates its length.

      Parameters

      • example: Example

        The example to be added.

      Returns Promise<void>

      Promise that resolves when the example has been added and its length calculated.

    • Calculates the lengths of the examples.

      Parameters

      Returns Promise<number[]>

      Promise that resolves with an array of lengths of the examples.

    • Selects examples until the total length of the selected examples reaches the maxLength.

      Parameters

      • inputVariables: Example

        The input variables for the examples.

      Returns Promise<Example[]>

      Promise that resolves with an array of selected examples.

    • The name of the serializable. Override to provide an alias or to preserve the serialized module name in minified environments.

      Implemented as a static method to support loading logic.

      Returns string

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