Nous.PromptTemplate (nous v0.13.3)
View SourceEEx-based prompt templates for building messages.
Supports variable substitution, role assignment, and composition of messages for agent interactions.
Simple Usage
template = PromptTemplate.from_template(
"You are a <%= @role %> assistant that speaks <%= @language %>.",
role: :system
)
message = PromptTemplate.to_message(template, %{role: "helpful", language: "Spanish"})
# => %Message{role: :system, content: "You are a helpful assistant that speaks Spanish."}Building Message Lists
messages = PromptTemplate.to_messages([
PromptTemplate.from_template("You are <%= @persona %>", role: :system),
PromptTemplate.from_template("Tell me about <%= @topic %>", role: :user)
], %{persona: "a historian", topic: "ancient Rome"})
# Use with Agent.run
Agent.run(agent, messages: messages)Default Values
template = PromptTemplate.from_template(
"Search for <%= @query %> with limit <%= @limit %>",
inputs: %{limit: 10}
)
# Only need to provide query, limit has a default
formatted = PromptTemplate.format(template, %{query: "elixir"})
# => "Search for elixir with limit 10"Conditional Content
Since templates use EEx, you can use conditionals:
template = PromptTemplate.from_template("""
You are a helpful assistant.
<%= if @include_tools do %>
You have access to these tools: <%= @tools %>
<% end %>
""")String Templates
For simple string templates without Message conversion:
text = PromptTemplate.format_string(
"Hello, <%= @name %>!",
%{name: "World"}
)
# => "Hello, World!"Summary
Functions
Create an assistant message template.
Create messages from a list of role/content tuples with shared bindings.
Compose multiple templates into a single template.
Extract variable names from a template string.
Format template with variable substitution.
Format a string template directly without creating a PromptTemplate struct.
Create a template from a string with <%= @var %> placeholders.
Create a system message template.
Convert template to Message with variable substitution.
Convert list of templates and/or messages to messages.
Create a user message template.
Check if all required variables are present in bindings.
Extract all variable names from a template.
Types
Functions
Create an assistant message template.
Shorthand for from_template(text, role: :assistant).
Example
template = PromptTemplate.assistant("I understand you want <%= @action %>")@spec build_messages([{atom(), String.t()}], map()) :: [Nous.Message.t()]
Create messages from a list of role/content tuples with shared bindings.
Convenient for building message lists inline.
Example
messages = PromptTemplate.build_messages([
{:system, "You are a <%= @role %> assistant"},
{:user, "Hello, my name is <%= @name %>"}
], %{role: "helpful", name: "Alice"})Compose multiple templates into a single template.
Joins templates with the specified separator.
Example
intro = system("You are a helpful assistant.")
rules = system("Follow these rules: <%= @rules %>")
combined = compose([intro, rules], "\n\n")
# Creates a single :system template with both texts joinedExtract variable names from a template string.
Example
PromptTemplate.extract_variables("Hello <%= @name %>!")
# => [:name]Format template with variable substitution.
Merges provided bindings with default inputs (bindings take precedence).
Example
template = from_template("Hello, <%= @name %>!", inputs: %{name: "World"})
format(template, %{}) # => "Hello, World!"
format(template, %{name: "Elixir"}) # => "Hello, Elixir!"Format a string template directly without creating a PromptTemplate struct.
Example
PromptTemplate.format_string("Hello, <%= @name %>!", %{name: "World"})
# => "Hello, World!"Create a template from a string with <%= @var %> placeholders.
Options
:role- Message role (:system,:user,:assistant). Default::user:inputs- Default variable values. Default:%{}
Example
template = PromptTemplate.from_template(
"You are a <%= @role %> assistant.",
role: :system,
inputs: %{role: "helpful"}
)Create a system message template.
Shorthand for from_template(text, role: :system).
Example
template = PromptTemplate.system("You are a <%= @persona %>")@spec to_message(t(), map()) :: Nous.Message.t()
Convert template to Message with variable substitution.
Example
template = from_template("You are a <%= @role %> assistant", role: :system)
message = to_message(template, %{role: "helpful"})
# => %Message{role: :system, content: "You are a helpful assistant"}@spec to_messages([t() | Nous.Message.t()], map()) :: [Nous.Message.t()]
Convert list of templates and/or messages to messages.
Items can be:
%PromptTemplate{}- Will be formatted with bindings%Message{}- Passed through unchanged
Example
messages = to_messages([
PromptTemplate.system("You are <%= @persona %>"),
Message.user("Hello"),
PromptTemplate.user("Tell me about <%= @topic %>")
], %{persona: "helpful", topic: "Elixir"})Create a user message template.
Shorthand for from_template(text, role: :user).
Example
template = PromptTemplate.user("Tell me about <%= @topic %>")Check if all required variables are present in bindings.
Returns {:ok, bindings} if all variables are present,
or {:error, missing_vars} if some are missing.
Example
template = from_template("Hello <%= @name %>, age <%= @age %>")
validate_bindings(template, %{name: "Alice", age: 30})
# => {:ok, %{name: "Alice", age: 30}}
validate_bindings(template, %{name: "Alice"})
# => {:error, [:age]}Extract all variable names from a template.
Useful for validation or documentation.
Example
template = from_template("Hello <%= @name %>, you are <%= @age %> years old")
variables(template)
# => [:name, :age]