PromptTemplate class final

A prompt template for a language model.

A prompt template consists of a string template. It accepts a set of parameters from the user that can be used to generate a prompt for a language model.

Example:

final promptTemplate = PromptTemplate(
  inputVariables: ['product'],
  template: 'What is a good name for a company that makes {product}?',
);
final prompt = promptTemplate.formatPrompt({'product': 'colorful socks'});
final res = await llm.invoke(prompt);

Note: the default constructor does not validate the template. You can use PromptTemplate.validateTemplate to validate the template.

You can also use the following convenience factory constructors to create a prompt template:

• PromptTemplate.fromTemplate creates a prompt template from a string template automatically extracting the input variables.

final promptTemplate = PromptTemplate.fromTemplate(
  'What is a good name for a company that makes {product}?',
);

• PromptTemplate.fromExamples to create prompt templates from a list of examples.
• PromptTemplate.fromFile to create a prompt template from a file.

Inheritance

• Object
• Runnable<InputValues, BaseLangChainOptions, PromptValue>
• BasePromptTemplate
• PromptTemplate

Annotations

• @immutable

Constructors

PromptTemplate({required Set<String> inputVariables, PartialValues? partialVariables, required String template})

A prompt template for a language model.

const

PromptTemplate.fromExamples({required List<String> examples, required String suffix, required Set<String> inputVariables, String exampleSeparator = '\n\n', String prefix = '', bool validateTemplate = true})

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

factory

PromptTemplate.fromTemplate(String template, {PartialValues? partialVariables, bool validateTemplate = true})

Creates a prompt template from a string template automatically extracting the input variables.

factory

Properties

defaultOptions → BaseLangChainOptions

The default options to use when invoking the Runnable.

final, inherited

hashCode → int

The hash code for this object.

no setter, override

inputVariables → Set<String>

A set of the names of the variables the prompt template expects.

final, inherited

partialVariables → PartialValues?

Partial variables.

final, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

template → String

The prompt template.

final

type → String

The type of the prompt template.

no setter, override

Methods

batch(List<InputValues> inputs, {List<BaseLangChainOptions>? options}) → Future<List<PromptValue>>

Batches the invocation of the Runnable on the given inputs.

inherited

bind(BaseLangChainOptions options) → RunnableBinding<InputValues, BaseLangChainOptions, PromptValue>

Binds the Runnable to the given options.

inherited

close() → void

Cleans up any resources associated with it the Runnable.

inherited

copyWith({Set<String>? inputVariables, Map<String, dynamic>? partialVariables, String? template}) → PromptTemplate

Copy the prompt template with the given parameters.

override

format([InputValues values = const {}]) → String

Format the prompt given the input values and return a formatted string.

override

formatPrompt(InputValues values) → PromptValue

Format the prompt given the input values and return a formatted prompt value.

override

getCompatibleOptions(RunnableOptions? options) → BaseLangChainOptions?

Returns the given options if they are compatible with the Runnable, otherwise returns null.

inherited

invoke(InputValues input, {BaseLangChainOptions? options}) → Future<PromptValue>

Format the prompt given the input values and return a formatted prompt value.

inherited

mergePartialAndUserVariables(Map<String, dynamic> userVariables) → Map<String, Object>

Merge the partial variables with the user variables.

inherited

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

partial(PartialValues values) → PromptTemplate

Return a partial of the prompt template.

override

pipe<NewRunOutput extends Object?, NewCallOptions extends RunnableOptions>(Runnable<PromptValue, NewCallOptions, NewRunOutput> next) → RunnableSequence<InputValues, NewRunOutput>

Pipes the output of this Runnable into another Runnable using a RunnableSequence.

inherited

stream(InputValues input, {BaseLangChainOptions? options}) → Stream<PromptValue>

Streams the output of invoking the Runnable on the given input.

inherited

streamFromInputStream(Stream<InputValues> inputStream, {BaseLangChainOptions? options}) → Stream<PromptValue>

Streams the output of invoking the Runnable on the given inputStream.

inherited

toString() → String

A string representation of this object.

override

validateTemplate() → void

Validate the integrity of the prompt template, checking that all the variables are present and that the right format is used.

override

withFallbacks(List<Runnable<InputValues, RunnableOptions, PromptValue>> fallbacks) → RunnableWithFallback<InputValues, PromptValue>

Adds fallback runnables to be invoked if the primary runnable fails.

inherited

withRetry({int maxRetries = 3, FutureOr<bool> retryIf(Object e)?, List<Duration?>? delayDurations, bool addJitter = false}) → RunnableRetry<InputValues, PromptValue>

Adds retry logic to an existing runnable.

inherited

Operators

operator ==(covariant PromptTemplate other) → bool

The equality operator.

override

Static Methods

fromFile(String templateFile, {PartialValues? partialVariables, bool validateTemplate = true}) → Future<PromptTemplate>

Loads a prompt from a file.