Class PromptTemplate<RunInput, PartialVariableName>

Schema to represent a basic prompt for an LLM.

Example

import { PromptTemplate } from "langchain/prompts";

const prompt = new PromptTemplate({
inputVariables: ["foo"],
template: "Say {foo}",
});

Type Parameters

  • RunInput extends InputValues = any

  • PartialVariableName extends string = any

Hierarchy

Implements

Constructors

Properties

PromptValueReturnType: StringPromptValueInterface
inputVariables: Extract<keyof RunInput, string>[]

A list of variable names the prompt template expects

partialVariables: PartialValues<PartialVariableName>

Partial variables

template: string

The prompt template

templateFormat: "f-string" = "f-string"

The format of the prompt template. Options are 'f-string'

Default Value

'f-string'

validateTemplate: boolean = true

Whether or not to try validating the template on initialization

Default Value

true

name?: string
outputParser?: BaseOutputParser<unknown>

How to parse the output of calling an LLM on this formatted prompt

Methods

  • Stream all output from a runnable, as reported to the callback system. This includes all inner runs of LLMs, Retrievers, Tools, etc. Output is streamed as Log objects, which include a list of jsonpatch ops that describe how the state of the run has changed in each step, and the final state of the run. The jsonpatch ops can be applied in order to construct state.

    Parameters

    Returns AsyncGenerator<RunLogPatch, any, unknown>

  • Bind lifecycle listeners to a Runnable, returning a new Runnable. The Run object contains information about the run, including its id, type, input, output, error, startTime, endTime, and any tags or metadata added to the run.

    Parameters

    • params: {
          onEnd?: ((run, config?) => void | Promise<void>);
          onError?: ((run, config?) => void | Promise<void>);
          onStart?: ((run, config?) => void | Promise<void>);
      }

      The object containing the callback functions.

      • Optional onEnd?: ((run, config?) => void | Promise<void>)
          • (run, config?): void | Promise<void>
          • Called after the runnable finishes running, with the Run object.

            Parameters

            Returns void | Promise<void>

      • Optional onError?: ((run, config?) => void | Promise<void>)
          • (run, config?): void | Promise<void>
          • Called if the runnable throws an error, with the Run object.

            Parameters

            Returns void | Promise<void>

      • Optional onStart?: ((run, config?) => void | Promise<void>)
          • (run, config?): void | Promise<void>
          • Called before the runnable starts running, with the Run object.

            Parameters

            Returns void | Promise<void>

    Returns Runnable<RunInput, StringPromptValueInterface, RunnableConfig>

  • Take examples in list format with prefix and suffix to create a prompt.

    Intended to be used a a way to dynamically create a prompt from examples.

    Parameters

    • examples: string[]

      List of examples to use in the prompt.

    • suffix: string

      String to go after the list of examples. Should generally set up the user's input.

    • inputVariables: string[]

      A list of variable names the final prompt template will expect

    • exampleSeparator: string = "\n\n"

      The separator to use in between examples

    • prefix: string = ""

      String that should go before any examples. Generally includes examples.

    Returns PromptTemplate<any, any>

    The final prompt template generated.

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