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:

final promptTemplate = PromptTemplate.fromTemplate(
  'What is a good name for a company that makes {product}?',
);
Inheritance
Available Extensions
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.
finalinherited
hashCode → int
The hash code for this object.
no setteroverride
inputVariables → Set<String>
A set of the names of the variables the prompt template expects.
finalinherited
partialVariables → PartialValues?
Partial variables.
finalinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
template → String
The prompt template.
final
type → String
The type of the prompt template.
no setteroverride

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

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.