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ChatPromptTemplate: Expand support for message formats and documentation (#8244)

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* Expands support for a variety of message formats in the
`from_messages` classmethod. Ideally, we could deprecate the other
on-ramps to reduce the amount of classmethods users need to know about.
* Expand documentation with code examples.
pull/8424/head
Eugene Yurtsev 1 year ago committed by GitHub
parent 61dd92f821
commit 760c278fe0
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2 changed files with 229 additions and 82 deletions
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231
libs/langchain/langchain/prompts/chat.py
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@ -261,63 +261,31 @@ class BaseChatPromptTemplate(BasePromptTemplate, ABC):
class ChatPromptTemplate(BaseChatPromptTemplate, ABC):
"""Use to create flexible templated prompts for chat models.
"""A prompt template for a chat models.
Examples:
Use to create flexible templated prompts for chat models.
Instantiation from role strings:
Examples:
.. code-block:: python
from langchain.prompts import ChatPromptTemplate
prompt_template = ChatPromptTemplate.from_role_strings(
[
('system', "You are a helpful bot. Your name is {bot_name}."),
('human', "{user_input}")
]
)
prompt_template.format_messages(
bot_name="bobby",
user_input="Hello! What is your name?"
)
Instantiation from messages:
This is useful if it's important to distinguish between messages that
are templates and messages that are already formatted.
.. code-block:: python
from langchain.prompts import (
ChatPromptTemplate,
HumanMessagePromptTemplate,
SystemMessagePromptTemplate,
)
from langchain.schema import AIMessage
prompt_template = ChatPromptTemplate.from_messages(
[
SystemMessagePromptTemplate.from_template(
"You are a helpful bot. Your name is {bot_name}."
),
AIMessage(content="Hello!"), # Already formatted message
HumanMessagePromptTemplate.from_template(
"{user_input}"
),
]
)
template = ChatPromptTemplate.from_messages([
("system", "You are a helpful AI bot. Your name is {name}."),
("human", "Hello, how are you doing?"),
("assistant", "I'm doing well, thanks!"),
("human", "{user_input}"),
])
prompt_template.format_messages(
bot_name="bobby",
user_input="Hello! What is your name?"
messages = template.format_messages(
name="Bob",
user_input="What is your name?"
)
"""
input_variables: List[str]
"""List of input variables."""
"""List of input variables in template messages. Used for validation."""
messages: List[
Union[BaseMessagePromptTemplate, BaseMessage, BaseChatPromptTemplate]
]
@ -390,11 +358,7 @@ class ChatPromptTemplate(BaseChatPromptTemplate, ABC):
def from_role_strings(
cls, string_messages: List[Tuple[str, str]]
) -> ChatPromptTemplate:
"""Create a class from a list of (role, template) tuples.
The roles "human", "ai", and "system" are special and will be converted
to the appropriate message class. All other roles will be converted to a
generic ChatMessagePromptTemplate.
"""Create a chat prompt template from a list of (role, template) tuples.
Args:
string_messages: list of (role, template) tuples.
@ -402,25 +366,18 @@ class ChatPromptTemplate(BaseChatPromptTemplate, ABC):
Returns:
a chat prompt template
"""
messages: List[BaseMessagePromptTemplate] = []
message: BaseMessagePromptTemplate
for role, template in string_messages:
if role == "human":
message = HumanMessagePromptTemplate.from_template(template)
elif role == "ai":
message = AIMessagePromptTemplate.from_template(template)
elif role == "system":
message = SystemMessagePromptTemplate.from_template(template)
else:
message = ChatMessagePromptTemplate.from_template(template, role=role)
messages.append(message)
return cls.from_messages(messages)
return cls(
messages=[
ChatMessagePromptTemplate.from_template(template, role=role)
for role, template in string_messages
]
)
@classmethod
def from_strings(
cls, string_messages: List[Tuple[Type[BaseMessagePromptTemplate], str]]
) -> ChatPromptTemplate:
"""Create a class from a list of (role class, template) tuples.
"""Create a chat prompt template from a list of (role class, template) tuples.
Args:
string_messages: list of (role class, template) tuples.
@ -428,29 +385,76 @@ class ChatPromptTemplate(BaseChatPromptTemplate, ABC):
Returns:
a chat prompt template
"""
messages = [
role(prompt=PromptTemplate.from_template(template))
for role, template in string_messages
]
return cls.from_messages(messages)
return cls.from_messages(string_messages)
@classmethod
def from_messages(
cls, messages: Sequence[Union[BaseMessagePromptTemplate, BaseMessage]]
cls,
messages: Sequence[
Union[
BaseMessagePromptTemplate,
BaseMessage,
Tuple[str, str],
Tuple[Type, str],
str,
]
],
) -> ChatPromptTemplate:
"""Create a chat template from a sequence of messages.
"""Create a chat prompt template from a variety of message formats.
Examples:
Instantiation from a list of role strings and 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?"),
])
Instantiation from a list 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."),
])
Args:
messages: sequence of templated or regular messages
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), (4) a string which is
shorthand for ("human", template); e.g., "{user_input}"
Returns:
a chat prompt template
"""
_messages = [_convert_to_message(message) for message in messages]
# Automatically infer input variables from messages
input_vars = set()
for message in messages:
if isinstance(message, BaseMessagePromptTemplate):
input_vars.update(message.input_variables)
return cls(input_variables=sorted(input_vars), messages=messages)
for _message in _messages:
if isinstance(_message, BaseMessagePromptTemplate):
input_vars.update(_message.input_variables)
return cls(input_variables=sorted(input_vars), messages=_messages)
def format(self, **kwargs: Any) -> str:
"""Format the chat template into a string.
@ -507,4 +511,77 @@ class ChatPromptTemplate(BaseChatPromptTemplate, ABC):
Args:
file_path: path to file.
"""
raise NotImplementedError
raise NotImplementedError()
def _create_template_from_message_type(
message_type: str, template: str
) -> 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.
Returns:
a message prompt template of the appropriate type.
"""
if message_type == "human":
message: BaseMessagePromptTemplate = HumanMessagePromptTemplate.from_template(
template
)
elif message_type == "ai":
message = AIMessagePromptTemplate.from_template(template)
elif message_type == "system":
message = SystemMessagePromptTemplate.from_template(template)
else:
raise ValueError(
f"Unexpected message type: {message_type}. Use one of 'human', 'ai', "
f"or 'system'."
)
return message
def _convert_to_message(
message: Union[
BaseMessagePromptTemplate,
BaseMessage,
Tuple[str, str],
Tuple[Type, str],
str,
]
) -> Union[BaseMessage, BaseMessagePromptTemplate]:
"""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
Returns:
an instance of a message or a message template
"""
if isinstance(message, BaseMessagePromptTemplate):
_message: Union[BaseMessage, BaseMessagePromptTemplate] = message
elif isinstance(message, BaseMessage):
_message = message
elif isinstance(message, str):
_message = _create_template_from_message_type("human", message)
elif isinstance(message, tuple):
if len(message) != 2:
raise ValueError(f"Expected 2-tuple of (role, template), got {message}")
message_type_str, template = message
if isinstance(message_type_str, str):
_message = _create_template_from_message_type(message_type_str, template)
else:
_message = message_type_str(prompt=PromptTemplate.from_template(template))
else:
raise NotImplementedError(f"Unsupported message type: {type(message)}")
return _message

80
libs/langchain/tests/unit_tests/prompts/test_chat.py
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@ -1,5 +1,5 @@
from pathlib import Path
from typing import List, Union
from typing import Any, List, Union
import pytest
@ -13,6 +13,7 @@ from langchain.prompts.chat import (
ChatPromptValue,
HumanMessagePromptTemplate,
SystemMessagePromptTemplate,
_convert_to_message,
)
from langchain.schema.messages import (
AIMessage,
@ -138,6 +139,33 @@ def test_chat_prompt_template_from_messages() -> None:
assert len(chat_prompt_template.messages) == 4
def test_chat_prompt_template_from_messages_using_role_strings() -> None:
"""Test creating a chat prompt template from role string messages."""
template = ChatPromptTemplate.from_messages(
[
("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}"),
]
)
messages = template.format_messages(name="Bob", user_input="What is your name?")
assert messages == [
SystemMessage(
content="You are a helpful AI bot. Your name is Bob.", additional_kwargs={}
),
HumanMessage(
content="Hello, how are you doing?", additional_kwargs={}, example=False
),
AIMessage(
content="I'm doing well, thanks!", additional_kwargs={}, example=False
),
HumanMessage(content="What is your name?", additional_kwargs={}, example=False),
]
def test_chat_prompt_template_with_messages() -> None:
messages: List[
Union[BaseMessagePromptTemplate, BaseMessage]
@ -205,7 +233,7 @@ def test_chat_from_role_strings() -> None:
template = ChatPromptTemplate.from_role_strings(
[
("system", "You are a bot."),
("ai", "hello!"),
("assistant", "hello!"),
("human", "{question}"),
("other", "{quack}"),
]
@ -213,8 +241,50 @@ def test_chat_from_role_strings() -> None:
messages = template.format_messages(question="How are you?", quack="duck")
assert messages == [
SystemMessage(content="You are a bot."),
AIMessage(content="hello!"),
HumanMessage(content="How are you?"),
ChatMessage(content="You are a bot.", role="system"),
ChatMessage(content="hello!", role="assistant"),
ChatMessage(content="How are you?", role="human"),
ChatMessage(content="duck", role="other"),
]
@pytest.mark.parametrize(
"args,expected",
[
(
("human", "{question}"),
HumanMessagePromptTemplate(
prompt=PromptTemplate.from_template("{question}")
),
),
(
"{question}",
HumanMessagePromptTemplate(
prompt=PromptTemplate.from_template("{question}")
),
),
(HumanMessage(content="question"), HumanMessage(content="question")),
(
HumanMessagePromptTemplate(
prompt=PromptTemplate.from_template("{question}")
),
HumanMessagePromptTemplate(
prompt=PromptTemplate.from_template("{question}")
),
),
],
)
def test_convert_to_message(
args: Any, expected: Union[BaseMessage, BaseMessagePromptTemplate]
) -> None:
"""Test convert to message."""
assert _convert_to_message(args) == expected
def test_convert_to_message_is_strict() -> None:
"""Verify that _convert_to_message is strict."""
with pytest.raises(ValueError):
# meow does not correspond to a valid message type.
# this test is here to ensure that functionality to interpret `meow`
# as a role is NOT added.
_convert_to_message(("meow", "question"))

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