"""Chat prompt template."""
from __future__ import annotations
from abc import ABC, abstractmethod
from collections.abc import Sequence
from pathlib import Path
from typing import (
Annotated,
Any,
Optional,
TypedDict,
TypeVar,
Union,
cast,
overload,
)
from pydantic import (
Field,
PositiveInt,
SkipValidation,
model_validator,
)
from langchain_core._api import deprecated
from langchain_core.load import Serializable
from langchain_core.messages import (
AIMessage,
AnyMessage,
BaseMessage,
ChatMessage,
HumanMessage,
SystemMessage,
convert_to_messages,
)
from langchain_core.messages.base import get_msg_title_repr
from langchain_core.prompt_values import ChatPromptValue, ImageURL, PromptValue
from langchain_core.prompts.base import BasePromptTemplate
from langchain_core.prompts.image import ImagePromptTemplate
from langchain_core.prompts.prompt import PromptTemplate
from langchain_core.prompts.string import (
PromptTemplateFormat,
StringPromptTemplate,
get_template_variables,
)
from langchain_core.utils import get_colored_text
from langchain_core.utils.interactive_env import is_interactive_env
[docs]
class BaseMessagePromptTemplate(Serializable, ABC):
"""Base class for message prompt templates."""
@classmethod
def is_lc_serializable(cls) -> bool:
"""Return whether or not the class is serializable.
Returns: True"""
return True
@classmethod
def get_lc_namespace(cls) -> list[str]:
"""Get the namespace of the langchain object."""
return ["langchain", "prompts", "chat"]
@property
@abstractmethod
def input_variables(self) -> list[str]:
"""Input variables for this prompt template.
Returns:
List of input variables.
"""
[docs]
def pretty_repr(self, html: bool = False) -> str:
"""Human-readable representation.
Args:
html: Whether to format as HTML. Defaults to False.
Returns:
Human-readable representation.
"""
raise NotImplementedError
[docs]
def pretty_print(self) -> None:
"""Print a human-readable representation."""
print(self.pretty_repr(html=is_interactive_env())) # noqa: T201
def __add__(self, other: Any) -> ChatPromptTemplate:
"""Combine two prompt templates.
Args:
other: Another prompt template.
Returns:
Combined prompt template.
"""
prompt = ChatPromptTemplate(messages=[self]) # type: ignore[call-arg]
return prompt + other
[docs]
class MessagesPlaceholder(BaseMessagePromptTemplate):
"""Prompt template that assumes variable is already list of messages.
A placeholder which can be used to pass in a list of messages.
Direct usage:
.. code-block:: python
from langchain_core.prompts import MessagesPlaceholder
prompt = MessagesPlaceholder("history")
prompt.format_messages() # raises KeyError
prompt = MessagesPlaceholder("history", optional=True)
prompt.format_messages() # returns empty list []
prompt.format_messages(
history=[
("system", "You are an AI assistant."),
("human", "Hello!"),
]
)
# -> [
# SystemMessage(content="You are an AI assistant."),
# HumanMessage(content="Hello!"),
# ]
Building a prompt with chat history:
.. code-block:: python
from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
prompt = ChatPromptTemplate.from_messages(
[
("system", "You are a helpful assistant."),
MessagesPlaceholder("history"),
("human", "{question}")
]
)
prompt.invoke(
{
"history": [("human", "what's 5 + 2"), ("ai", "5 + 2 is 7")],
"question": "now multiply that by 4"
}
)
# -> ChatPromptValue(messages=[
# SystemMessage(content="You are a helpful assistant."),
# HumanMessage(content="what's 5 + 2"),
# AIMessage(content="5 + 2 is 7"),
# HumanMessage(content="now multiply that by 4"),
# ])
Limiting the number of messages:
.. code-block:: python
from langchain_core.prompts import MessagesPlaceholder
prompt = MessagesPlaceholder("history", n_messages=1)
prompt.format_messages(
history=[
("system", "You are an AI assistant."),
("human", "Hello!"),
]
)
# -> [
# HumanMessage(content="Hello!"),
# ]
"""
variable_name: str
"""Name of variable to use as messages."""
optional: bool = False
"""If True format_messages can be called with no arguments and will return an empty
list. If False then a named argument with name `variable_name` must be passed
in, even if the value is an empty list."""
n_messages: Optional[PositiveInt] = None
"""Maximum number of messages to include. If None, then will include all.
Defaults to None."""
@classmethod
def get_lc_namespace(cls) -> list[str]:
"""Get the namespace of the langchain object."""
return ["langchain", "prompts", "chat"]
def __init__(
self, variable_name: str, *, optional: bool = False, **kwargs: Any
) -> None:
# mypy can't detect the init which is defined in the parent class
# b/c these are BaseModel classes.
super().__init__( # type: ignore
variable_name=variable_name, optional=optional, **kwargs
)
@property
def input_variables(self) -> list[str]:
"""Input variables for this prompt template.
Returns:
List of input variable names.
"""
return [self.variable_name] if not self.optional else []
[docs]
def pretty_repr(self, html: bool = False) -> str:
"""Human-readable representation.
Args:
html: Whether to format as HTML. Defaults to False.
Returns:
Human-readable representation.
"""
var = "{" + self.variable_name + "}"
if html:
title = get_msg_title_repr("Messages Placeholder", bold=True)
var = get_colored_text(var, "yellow")
else:
title = get_msg_title_repr("Messages Placeholder")
return f"{title}\n\n{var}"
MessagePromptTemplateT = TypeVar(
"MessagePromptTemplateT", bound="BaseStringMessagePromptTemplate"
)
"""Type variable for message prompt templates."""
[docs]
class BaseStringMessagePromptTemplate(BaseMessagePromptTemplate, ABC):
"""Base class for message prompt templates that use a string prompt template."""
prompt: StringPromptTemplate
"""String prompt template."""
additional_kwargs: dict = Field(default_factory=dict)
"""Additional keyword arguments to pass to the prompt template."""
@classmethod
def get_lc_namespace(cls) -> list[str]:
"""Get the namespace of the langchain object."""
return ["langchain", "prompts", "chat"]
[docs]
@classmethod
def from_template(
cls: type[MessagePromptTemplateT],
template: str,
template_format: PromptTemplateFormat = "f-string",
partial_variables: Optional[dict[str, Any]] = None,
**kwargs: Any,
) -> MessagePromptTemplateT:
"""Create a class from a string template.
Args:
template: a template.
template_format: format of the template. Defaults to "f-string".
partial_variables: A dictionary of variables that can be used to partially
fill in the template. For example, if the template is
`"{variable1} {variable2}"`, and `partial_variables` is
`{"variable1": "foo"}`, then the final prompt will be
`"foo {variable2}"`.
Defaults to None.
**kwargs: keyword arguments to pass to the constructor.
Returns:
A new instance of this class.
"""
prompt = PromptTemplate.from_template(
template,
template_format=template_format,
partial_variables=partial_variables,
)
return cls(prompt=prompt, **kwargs)
[docs]
@classmethod
def from_template_file(
cls: type[MessagePromptTemplateT],
template_file: Union[str, Path],
input_variables: list[str],
**kwargs: Any,
) -> MessagePromptTemplateT:
"""Create a class from a template file.
Args:
template_file: path to a template file. String or Path.
input_variables: list of input variables.
**kwargs: keyword arguments to pass to the constructor.
Returns:
A new instance of this class.
"""
prompt = PromptTemplate.from_file(template_file, input_variables)
return cls(prompt=prompt, **kwargs)
@property
def input_variables(self) -> list[str]:
"""
Input variables for this prompt template.
Returns:
List of input variable names.
"""
return self.prompt.input_variables
[docs]
def pretty_repr(self, html: bool = False) -> str:
"""Human-readable representation.
Args:
html: Whether to format as HTML. Defaults to False.
Returns:
Human-readable representation.
"""
# TODO: Handle partials
title = self.__class__.__name__.replace("MessagePromptTemplate", " Message")
title = get_msg_title_repr(title, bold=html)
return f"{title}\n\n{self.prompt.pretty_repr(html=html)}"
[docs]
class ChatMessagePromptTemplate(BaseStringMessagePromptTemplate):
"""Chat message prompt template."""
role: str
"""Role of the message."""
@classmethod
def get_lc_namespace(cls) -> list[str]:
"""Get the namespace of the langchain object."""
return ["langchain", "prompts", "chat"]
_StringImageMessagePromptTemplateT = TypeVar(
"_StringImageMessagePromptTemplateT", bound="_StringImageMessagePromptTemplate"
)
class _TextTemplateParam(TypedDict, total=False):
text: Union[str, dict]
class _ImageTemplateParam(TypedDict, total=False):
image_url: Union[str, dict]
class _StringImageMessagePromptTemplate(BaseMessagePromptTemplate):
"""Human message prompt template. This is a message sent from the user."""
prompt: Union[
StringPromptTemplate, list[Union[StringPromptTemplate, ImagePromptTemplate]]
]
"""Prompt template."""
additional_kwargs: dict = Field(default_factory=dict)
"""Additional keyword arguments to pass to the prompt template."""
_msg_class: type[BaseMessage]
@classmethod
def get_lc_namespace(cls) -> list[str]:
"""Get the namespace of the langchain object."""
return ["langchain", "prompts", "chat"]
@classmethod
def from_template(
cls: type[_StringImageMessagePromptTemplateT],
template: Union[str, list[Union[str, _TextTemplateParam, _ImageTemplateParam]]],
template_format: PromptTemplateFormat = "f-string",
*,
partial_variables: Optional[dict[str, Any]] = None,
**kwargs: Any,
) -> _StringImageMessagePromptTemplateT:
"""Create a class from a string template.
Args:
template: a template.
template_format: format of the template.
Options are: 'f-string', 'mustache', 'jinja2'. Defaults to "f-string".
partial_variables: A dictionary of variables that can be used too partially.
Defaults to None.
**kwargs: keyword arguments to pass to the constructor.
Returns:
A new instance of this class.
Raises:
ValueError: If the template is not a string or list of strings.
"""
if isinstance(template, str):
prompt: Union[StringPromptTemplate, list] = PromptTemplate.from_template(
template,
template_format=template_format,
partial_variables=partial_variables,
)
return cls(prompt=prompt, **kwargs)
elif isinstance(template, list):
if (partial_variables is not None) and len(partial_variables) > 0:
msg = "Partial variables are not supported for list of templates."
raise ValueError(msg)
prompt = []
for tmpl in template:
if isinstance(tmpl, str) or isinstance(tmpl, dict) and "text" in tmpl:
if isinstance(tmpl, str):
text: str = tmpl
else:
text = cast(_TextTemplateParam, tmpl)["text"] # type: ignore[assignment]
prompt.append(
PromptTemplate.from_template(
text, template_format=template_format
)
)
elif isinstance(tmpl, dict) and "image_url" in tmpl:
img_template = cast(_ImageTemplateParam, tmpl)["image_url"]
input_variables = []
if isinstance(img_template, str):
vars = get_template_variables(img_template, template_format)
if vars:
if len(vars) > 1:
msg = (
"Only one format variable allowed per image"
f" template.\nGot: {vars}"
f"\nFrom: {tmpl}"
)
raise ValueError(msg)
input_variables = [vars[0]]
img_template = {"url": img_template}
img_template_obj = ImagePromptTemplate(
input_variables=input_variables,
template=img_template,
template_format=template_format,
)
elif isinstance(img_template, dict):
img_template = dict(img_template)
for key in ["url", "path", "detail"]:
if key in img_template:
input_variables.extend(
get_template_variables(
img_template[key], template_format
)
)
img_template_obj = ImagePromptTemplate(
input_variables=input_variables,
template=img_template,
template_format=template_format,
)
else:
msg = f"Invalid image template: {tmpl}"
raise ValueError(msg)
prompt.append(img_template_obj)
else:
msg = f"Invalid template: {tmpl}"
raise ValueError(msg)
return cls(prompt=prompt, **kwargs)
else:
msg = f"Invalid template: {template}"
raise ValueError(msg)
@classmethod
def from_template_file(
cls: type[_StringImageMessagePromptTemplateT],
template_file: Union[str, Path],
input_variables: list[str],
**kwargs: Any,
) -> _StringImageMessagePromptTemplateT:
"""Create a class from a template file.
Args:
template_file: path to a template file. String or Path.
input_variables: list of input variables.
**kwargs: keyword arguments to pass to the constructor.
Returns:
A new instance of this class.
"""
with open(str(template_file)) as f:
template = f.read()
return cls.from_template(template, input_variables=input_variables, **kwargs)
def format_messages(self, **kwargs: Any) -> list[BaseMessage]:
"""Format messages from kwargs.
Args:
**kwargs: Keyword arguments to use for formatting.
Returns:
List of BaseMessages.
"""
return [self.format(**kwargs)]
async def aformat_messages(self, **kwargs: Any) -> list[BaseMessage]:
"""Async format messages from kwargs.
Args:
**kwargs: Keyword arguments to use for formatting.
Returns:
List of BaseMessages.
"""
return [await self.aformat(**kwargs)]
@property
def input_variables(self) -> list[str]:
"""
Input variables for this prompt template.
Returns:
List of input variable names.
"""
prompts = self.prompt if isinstance(self.prompt, list) else [self.prompt]
input_variables = [iv for prompt in prompts for iv in prompt.input_variables]
return input_variables
def format(self, **kwargs: Any) -> BaseMessage:
"""Format the prompt template.
Args:
**kwargs: Keyword arguments to use for formatting.
Returns:
Formatted message.
"""
if isinstance(self.prompt, StringPromptTemplate):
text = self.prompt.format(**kwargs)
return self._msg_class(
content=text, additional_kwargs=self.additional_kwargs
)
else:
content: list = []
for prompt in self.prompt:
inputs = {var: kwargs[var] for var in prompt.input_variables}
if isinstance(prompt, StringPromptTemplate):
formatted: Union[str, ImageURL] = prompt.format(**inputs)
content.append({"type": "text", "text": formatted})
elif isinstance(prompt, ImagePromptTemplate):
formatted = prompt.format(**inputs)
content.append({"type": "image_url", "image_url": formatted})
return self._msg_class(
content=content, additional_kwargs=self.additional_kwargs
)
async def aformat(self, **kwargs: Any) -> BaseMessage:
"""Async format the prompt template.
Args:
**kwargs: Keyword arguments to use for formatting.
Returns:
Formatted message.
"""
if isinstance(self.prompt, StringPromptTemplate):
text = await self.prompt.aformat(**kwargs)
return self._msg_class(
content=text, additional_kwargs=self.additional_kwargs
)
else:
content: list = []
for prompt in self.prompt:
inputs = {var: kwargs[var] for var in prompt.input_variables}
if isinstance(prompt, StringPromptTemplate):
formatted: Union[str, ImageURL] = await prompt.aformat(**inputs)
content.append({"type": "text", "text": formatted})
elif isinstance(prompt, ImagePromptTemplate):
formatted = await prompt.aformat(**inputs)
content.append({"type": "image_url", "image_url": formatted})
return self._msg_class(
content=content, additional_kwargs=self.additional_kwargs
)
def pretty_repr(self, html: bool = False) -> str:
"""Human-readable representation.
Args:
html: Whether to format as HTML. Defaults to False.
Returns:
Human-readable representation.
"""
# TODO: Handle partials
title = self.__class__.__name__.replace("MessagePromptTemplate", " Message")
title = get_msg_title_repr(title, bold=html)
prompts = self.prompt if isinstance(self.prompt, list) else [self.prompt]
prompt_reprs = "\n\n".join(prompt.pretty_repr(html=html) for prompt in prompts)
return f"{title}\n\n{prompt_reprs}"
[docs]
class HumanMessagePromptTemplate(_StringImageMessagePromptTemplate):
"""Human message prompt template. This is a message sent from the user."""
_msg_class: type[BaseMessage] = HumanMessage
[docs]
class AIMessagePromptTemplate(_StringImageMessagePromptTemplate):
"""AI message prompt template. This is a message sent from the AI."""
_msg_class: type[BaseMessage] = AIMessage
@classmethod
def get_lc_namespace(cls) -> list[str]:
"""Get the namespace of the langchain object."""
return ["langchain", "prompts", "chat"]
[docs]
class SystemMessagePromptTemplate(_StringImageMessagePromptTemplate):
"""System message prompt template.
This is a message that is not sent to the user.
"""
_msg_class: type[BaseMessage] = SystemMessage
@classmethod
def get_lc_namespace(cls) -> list[str]:
"""Get the namespace of the langchain object."""
return ["langchain", "prompts", "chat"]
[docs]
class BaseChatPromptTemplate(BasePromptTemplate, ABC):
"""Base class for chat prompt templates."""
@property
def lc_attributes(self) -> dict:
"""
Return a list of attribute names that should be included in the
serialized kwargs. These attributes must be accepted by the
constructor.
"""
return {"input_variables": self.input_variables}
[docs]
def pretty_repr(self, html: bool = False) -> str:
"""Human-readable representation.
Args:
html: Whether to format as HTML. Defaults to False.
Returns:
Human-readable representation.
"""
raise NotImplementedError
[docs]
def pretty_print(self) -> None:
"""Print a human-readable representation."""
print(self.pretty_repr(html=is_interactive_env())) # noqa: T201
MessageLike = Union[BaseMessagePromptTemplate, BaseMessage, BaseChatPromptTemplate]
MessageLikeRepresentation = Union[
MessageLike,
tuple[
Union[str, type],
Union[str, list[dict], list[object]],
],
str,
]
[docs]
class ChatPromptTemplate(BaseChatPromptTemplate):
"""Prompt template for chat models.
Use to create flexible templated prompts for chat models.
Examples:
.. versionchanged:: 0.2.24
You can pass any Message-like formats supported by
``ChatPromptTemplate.from_messages()`` directly to ``ChatPromptTemplate()``
init.
.. code-block:: python
from langchain_core.prompts import ChatPromptTemplate
template = ChatPromptTemplate([
("system", "You are a helpful AI bot. Your name is {name}."),
("human", "Hello, how are you doing?"),
("ai", "I'm doing well, thanks!"),
("human", "{user_input}"),
])
prompt_value = template.invoke(
{
"name": "Bob",
"user_input": "What is your name?"
}
)
# Output:
# ChatPromptValue(
# messages=[
# SystemMessage(content='You are a helpful AI bot. Your name is Bob.'),
# HumanMessage(content='Hello, how are you doing?'),
# AIMessage(content="I'm doing well, thanks!"),
# HumanMessage(content='What is your name?')
# ]
#)
Messages Placeholder:
.. code-block:: python
# In addition to Human/AI/Tool/Function messages,
# you can initialize the template with a MessagesPlaceholder
# either using the class directly or with the shorthand tuple syntax:
template = ChatPromptTemplate([
("system", "You are a helpful AI bot."),
# Means the template will receive an optional list of messages under
# the "conversation" key
("placeholder", "{conversation}")
# Equivalently:
# MessagesPlaceholder(variable_name="conversation", optional=True)
])
prompt_value = template.invoke(
{
"conversation": [
("human", "Hi!"),
("ai", "How can I assist you today?"),
("human", "Can you make me an ice cream sundae?"),
("ai", "No.")
]
}
)
# Output:
# ChatPromptValue(
# messages=[
# SystemMessage(content='You are a helpful AI bot.'),
# HumanMessage(content='Hi!'),
# AIMessage(content='How can I assist you today?'),
# HumanMessage(content='Can you make me an ice cream sundae?'),
# AIMessage(content='No.'),
# ]
#)
Single-variable template:
If your prompt has only a single input variable (i.e., 1 instance of "{variable_nams}"),
and you invoke the template with a non-dict object, the prompt template will
inject the provided argument into that variable location.
.. code-block:: python
from langchain_core.prompts import ChatPromptTemplate
template = ChatPromptTemplate([
("system", "You are a helpful AI bot. Your name is Carl."),
("human", "{user_input}"),
])
prompt_value = template.invoke("Hello, there!")
# Equivalent to
# prompt_value = template.invoke({"user_input": "Hello, there!"})
# Output:
# ChatPromptValue(
# messages=[
# SystemMessage(content='You are a helpful AI bot. Your name is Carl.'),
# HumanMessage(content='Hello, there!'),
# ]
# )
""" # noqa: E501
messages: Annotated[list[MessageLike], SkipValidation()]
"""List of messages consisting of either message prompt templates or messages."""
validate_template: bool = False
"""Whether or not to try validating the template."""
def __init__(
self,
messages: Sequence[MessageLikeRepresentation],
*,
template_format: PromptTemplateFormat = "f-string",
**kwargs: Any,
) -> None:
"""Create a chat prompt template from a variety of message formats.
Args:
messages: sequence of message representations.
A message can be represented using the following formats:
(1) BaseMessagePromptTemplate, (2) BaseMessage, (3) 2-tuple of
(message type, template); e.g., ("human", "{user_input}"),
(4) 2-tuple of (message class, template), (5) a string which is
shorthand for ("human", template); e.g., "{user_input}".
template_format: format of the template. Defaults to "f-string".
input_variables: A list of the names of the variables whose values are
required as inputs to the prompt.
optional_variables: A list of the names of the variables for placeholder
or MessagePlaceholder that are optional. These variables are auto inferred
from the prompt and user need not provide them.
partial_variables: A dictionary of the partial variables the prompt
template carries. Partial variables populate the template so that you
don't need to pass them in every time you call the prompt.
validate_template: Whether to validate the template.
input_types: A dictionary of the types of the variables the prompt template
expects. If not provided, all variables are assumed to be strings.
Returns:
A chat prompt template.
Examples:
Instantiation from a list of message templates:
.. code-block:: python
template = ChatPromptTemplate([
("human", "Hello, how are you?"),
("ai", "I'm doing well, thanks!"),
("human", "That's good to hear."),
])
Instantiation from mixed message formats:
.. code-block:: python
template = ChatPromptTemplate([
SystemMessage(content="hello"),
("human", "Hello, how are you?"),
])
"""
_messages = [
_convert_to_message(message, template_format) for message in messages
]
# Automatically infer input variables from messages
input_vars: set[str] = set()
optional_variables: set[str] = set()
partial_vars: dict[str, Any] = {}
for _message in _messages:
if isinstance(_message, MessagesPlaceholder) and _message.optional:
partial_vars[_message.variable_name] = []
optional_variables.add(_message.variable_name)
elif isinstance(
_message, (BaseChatPromptTemplate, BaseMessagePromptTemplate)
):
input_vars.update(_message.input_variables)
kwargs = {
"input_variables": sorted(input_vars),
"optional_variables": sorted(optional_variables),
"partial_variables": partial_vars,
**kwargs,
}
cast(type[ChatPromptTemplate], super()).__init__(messages=_messages, **kwargs)
@classmethod
def get_lc_namespace(cls) -> list[str]:
"""Get the namespace of the langchain object."""
return ["langchain", "prompts", "chat"]
def __add__(self, other: Any) -> ChatPromptTemplate:
"""Combine two prompt templates.
Args:
other: Another prompt template.
Returns:
Combined prompt template.
"""
# Allow for easy combining
if isinstance(other, ChatPromptTemplate):
return ChatPromptTemplate(messages=self.messages + other.messages) # type: ignore[call-arg]
elif isinstance(
other, (BaseMessagePromptTemplate, BaseMessage, BaseChatPromptTemplate)
):
return ChatPromptTemplate(messages=self.messages + [other]) # type: ignore[call-arg]
elif isinstance(other, (list, tuple)):
_other = ChatPromptTemplate.from_messages(other)
return ChatPromptTemplate(messages=self.messages + _other.messages) # type: ignore[call-arg]
elif isinstance(other, str):
prompt = HumanMessagePromptTemplate.from_template(other)
return ChatPromptTemplate(messages=self.messages + [prompt]) # type: ignore[call-arg]
else:
msg = f"Unsupported operand type for +: {type(other)}"
raise NotImplementedError(msg)
@model_validator(mode="before")
@classmethod
def validate_input_variables(cls, values: dict) -> Any:
"""Validate input variables.
If input_variables is not set, it will be set to the union of
all input variables in the messages.
Args:
values: values to validate.
Returns:
Validated values.
Raises:
ValueError: If input variables do not match.
"""
messages = values["messages"]
input_vars = set()
optional_variables = set()
input_types: dict[str, Any] = values.get("input_types", {})
for message in messages:
if isinstance(message, (BaseMessagePromptTemplate, BaseChatPromptTemplate)):
input_vars.update(message.input_variables)
if isinstance(message, MessagesPlaceholder):
if "partial_variables" not in values:
values["partial_variables"] = {}
if (
message.optional
and message.variable_name not in values["partial_variables"]
):
values["partial_variables"][message.variable_name] = []
optional_variables.add(message.variable_name)
if message.variable_name not in input_types:
input_types[message.variable_name] = list[AnyMessage]
if "partial_variables" in values:
input_vars = input_vars - set(values["partial_variables"])
if optional_variables:
input_vars = input_vars - optional_variables
if "input_variables" in values and values.get("validate_template"):
if input_vars != set(values["input_variables"]):
msg = (
"Got mismatched input_variables. "
f"Expected: {input_vars}. "
f"Got: {values['input_variables']}"
)
raise ValueError(msg)
else:
values["input_variables"] = sorted(input_vars)
if optional_variables:
values["optional_variables"] = sorted(optional_variables)
values["input_types"] = input_types
return values
[docs]
@classmethod
def from_template(cls, template: str, **kwargs: Any) -> ChatPromptTemplate:
"""Create a chat prompt template from a template string.
Creates a chat template consisting of a single message assumed to be from
the human.
Args:
template: template string
**kwargs: keyword arguments to pass to the constructor.
Returns:
A new instance of this class.
"""
prompt_template = PromptTemplate.from_template(template, **kwargs)
message = HumanMessagePromptTemplate(prompt=prompt_template)
return cls.from_messages([message])
[docs]
@classmethod
@deprecated("0.0.1", alternative="from_messages classmethod", pending=True)
def from_role_strings(
cls, string_messages: list[tuple[str, str]]
) -> ChatPromptTemplate:
"""Create a chat prompt template from a list of (role, template) tuples.
Args:
string_messages: list of (role, template) tuples.
Returns:
a chat prompt template.
"""
return cls( # type: ignore[call-arg]
messages=[
ChatMessagePromptTemplate.from_template(template, role=role)
for role, template in string_messages
]
)
[docs]
@classmethod
@deprecated("0.0.1", alternative="from_messages classmethod", pending=True)
def from_strings(
cls, string_messages: list[tuple[type[BaseMessagePromptTemplate], str]]
) -> ChatPromptTemplate:
"""Create a chat prompt template from a list of (role class, template) tuples.
Args:
string_messages: list of (role class, template) tuples.
Returns:
a chat prompt template.
"""
return cls.from_messages(string_messages)
[docs]
@classmethod
def from_messages(
cls,
messages: Sequence[MessageLikeRepresentation],
template_format: PromptTemplateFormat = "f-string",
) -> ChatPromptTemplate:
"""Create a chat prompt template from a variety of message formats.
Examples:
Instantiation from a list of message templates:
.. code-block:: python
template = ChatPromptTemplate.from_messages([
("human", "Hello, how are you?"),
("ai", "I'm doing well, thanks!"),
("human", "That's good to hear."),
])
Instantiation from mixed message formats:
.. code-block:: python
template = ChatPromptTemplate.from_messages([
SystemMessage(content="hello"),
("human", "Hello, how are you?"),
])
Args:
messages: sequence of message representations.
A message can be represented using the following formats:
(1) BaseMessagePromptTemplate, (2) BaseMessage, (3) 2-tuple of
(message type, template); e.g., ("human", "{user_input}"),
(4) 2-tuple of (message class, template), (5) a string which is
shorthand for ("human", template); e.g., "{user_input}".
template_format: format of the template. Defaults to "f-string".
Returns:
a chat prompt template.
"""
return cls(messages, template_format=template_format)
[docs]
def partial(self, **kwargs: Any) -> ChatPromptTemplate:
"""Get a new ChatPromptTemplate with some input variables already filled in.
Args:
**kwargs: keyword arguments to use for filling in template variables. Ought
to be a subset of the input variables.
Returns:
A new ChatPromptTemplate.
Example:
.. code-block:: python
from langchain_core.prompts import ChatPromptTemplate
template = ChatPromptTemplate.from_messages(
[
("system", "You are an AI assistant named {name}."),
("human", "Hi I'm {user}"),
("ai", "Hi there, {user}, I'm {name}."),
("human", "{input}"),
]
)
template2 = template.partial(user="Lucy", name="R2D2")
template2.format_messages(input="hello")
"""
prompt_dict = self.__dict__.copy()
prompt_dict["input_variables"] = list(
set(self.input_variables).difference(kwargs)
)
prompt_dict["partial_variables"] = {**self.partial_variables, **kwargs}
return type(self)(**prompt_dict)
[docs]
def append(self, message: MessageLikeRepresentation) -> None:
"""Append a message to the end of the chat template.
Args:
message: representation of a message to append.
"""
self.messages.append(_convert_to_message(message))
[docs]
def extend(self, messages: Sequence[MessageLikeRepresentation]) -> None:
"""Extend the chat template with a sequence of messages.
Args:
messages: sequence of message representations to append.
"""
self.messages.extend([_convert_to_message(message) for message in messages])
@overload
def __getitem__(self, index: int) -> MessageLike: ...
@overload
def __getitem__(self, index: slice) -> ChatPromptTemplate: ...
def __getitem__(
self, index: Union[int, slice]
) -> Union[MessageLike, ChatPromptTemplate]:
"""Use to index into the chat template."""
if isinstance(index, slice):
start, stop, step = index.indices(len(self.messages))
messages = self.messages[start:stop:step]
return ChatPromptTemplate.from_messages(messages)
else:
return self.messages[index]
def __len__(self) -> int:
"""Get the length of the chat template."""
return len(self.messages)
@property
def _prompt_type(self) -> str:
"""Name of prompt type. Used for serialization."""
return "chat"
[docs]
def save(self, file_path: Union[Path, str]) -> None:
"""Save prompt to file.
Args:
file_path: path to file.
"""
raise NotImplementedError
[docs]
def pretty_repr(self, html: bool = False) -> str:
"""Human-readable representation.
Args:
html: Whether to format as HTML. Defaults to False.
Returns:
Human-readable representation.
"""
# TODO: handle partials
return "\n\n".join(msg.pretty_repr(html=html) for msg in self.messages)
def _create_template_from_message_type(
message_type: str,
template: Union[str, list],
template_format: PromptTemplateFormat = "f-string",
) -> BaseMessagePromptTemplate:
"""Create a message prompt template from a message type and template string.
Args:
message_type: str the type of the message template (e.g., "human", "ai", etc.)
template: str the template string.
template_format: format of the template. Defaults to "f-string".
Returns:
a message prompt template of the appropriate type.
Raises:
ValueError: If unexpected message type.
"""
if message_type in ("human", "user"):
message: BaseMessagePromptTemplate = HumanMessagePromptTemplate.from_template(
template, template_format=template_format
)
elif message_type in ("ai", "assistant"):
message = AIMessagePromptTemplate.from_template(
cast(str, template), template_format=template_format
)
elif message_type == "system":
message = SystemMessagePromptTemplate.from_template(
cast(str, template), template_format=template_format
)
elif message_type == "placeholder":
if isinstance(template, str):
if template[0] != "{" or template[-1] != "}":
msg = (
f"Invalid placeholder template: {template}."
" Expected a variable name surrounded by curly braces."
)
raise ValueError(msg)
var_name = template[1:-1]
message = MessagesPlaceholder(variable_name=var_name, optional=True)
elif len(template) == 2 and isinstance(template[1], bool):
var_name_wrapped, is_optional = template
if not isinstance(var_name_wrapped, str):
msg = (
"Expected variable name to be a string." f" Got: {var_name_wrapped}"
)
raise ValueError(msg)
if var_name_wrapped[0] != "{" or var_name_wrapped[-1] != "}":
msg = (
f"Invalid placeholder template: {var_name_wrapped}."
" Expected a variable name surrounded by curly braces."
)
raise ValueError(msg)
var_name = var_name_wrapped[1:-1]
message = MessagesPlaceholder(variable_name=var_name, optional=is_optional)
else:
msg = (
"Unexpected arguments for placeholder message type."
" Expected either a single string variable name"
" or a list of [variable_name: str, is_optional: bool]."
f" Got: {template}"
)
raise ValueError(msg)
else:
msg = (
f"Unexpected message type: {message_type}. Use one of 'human',"
f" 'user', 'ai', 'assistant', or 'system'."
)
raise ValueError(msg)
return message
def _convert_to_message(
message: MessageLikeRepresentation,
template_format: PromptTemplateFormat = "f-string",
) -> Union[BaseMessage, BaseMessagePromptTemplate, BaseChatPromptTemplate]:
"""Instantiate a message from a variety of message formats.
The message format can be one of the following:
- BaseMessagePromptTemplate
- BaseMessage
- 2-tuple of (role string, template); e.g., ("human", "{user_input}")
- 2-tuple of (message class, template)
- string: shorthand for ("human", template); e.g., "{user_input}"
Args:
message: a representation of a message in one of the supported formats.
template_format: format of the template. Defaults to "f-string".
Returns:
an instance of a message or a message template.
Raises:
ValueError: If unexpected message type.
ValueError: If 2-tuple does not have 2 elements.
"""
if isinstance(message, (BaseMessagePromptTemplate, BaseChatPromptTemplate)):
_message: Union[
BaseMessage, BaseMessagePromptTemplate, BaseChatPromptTemplate
] = message
elif isinstance(message, BaseMessage):
_message = message
elif isinstance(message, str):
_message = _create_template_from_message_type(
"human", message, template_format=template_format
)
elif isinstance(message, tuple):
if len(message) != 2:
msg = f"Expected 2-tuple of (role, template), got {message}"
raise ValueError(msg)
message_type_str, template = message
if isinstance(message_type_str, str):
_message = _create_template_from_message_type(
message_type_str, template, template_format=template_format
)
else:
_message = message_type_str(
prompt=PromptTemplate.from_template(
cast(str, template), template_format=template_format
)
)
else:
msg = f"Unsupported message type: {type(message)}"
raise NotImplementedError(msg)
return _message
