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from typing import List
import tiktoken
from langchain_core.messages import BaseMessage, ToolMessage, HumanMessage, AIMessage, SystemMessage, trim_messages
def str_token_counter(text: str) -> int:
enc = tiktoken.get_encoding("o200k_base")
return len(enc.encode(text))
def tiktoken_counter(messages: List[BaseMessage]) -> int:
"""Approximately reproduce https://github.com/openai/openai-cookbook/blob/main/examples/How_to_count_tokens_with_tiktoken.ipynb
For simplicity only supports str Message.contents.
"""
num_tokens = 3 # every reply is primed with <|start|>assistant<|message|>
tokens_per_message = 3
tokens_per_name = 1
for msg in messages:
if isinstance(msg, HumanMessage):
role = "user"
elif isinstance(msg, AIMessage):
role = "assistant"
elif isinstance(msg, ToolMessage):
role = "tool"
elif isinstance(msg, SystemMessage):
role = "system"
else:
raise ValueError(f"Unsupported messages type {msg.__class__}")
num_tokens += (
tokens_per_message
+ str_token_counter(role)
+ str_token_counter(msg.content)
)
if msg.name:
num_tokens += tokens_per_name + str_token_counter(msg.name)
return num_tokens
def convert_to_openai_messages(messages: List[BaseMessage]) -> List[dict]:
"""Convert LangChain messages to OpenAI format."""
openai_messages = []
for msg in messages:
message_dict = {"content": msg.content}
if isinstance(msg, HumanMessage):
message_dict["role"] = "user"
elif isinstance(msg, AIMessage):
message_dict["role"] = "assistant"
elif isinstance(msg, SystemMessage):
message_dict["role"] = "system"
elif isinstance(msg, ToolMessage):
message_dict["role"] = "tool"
else:
raise ValueError(f"Unsupported message type: {msg.__class__}")
if msg.name:
message_dict["name"] = msg.name
openai_messages.append(message_dict)
return openai_messages
def trim_messages_openai(messages: List[BaseMessage]) -> List[dict]:
"""Trim LangChain messages and convert to OpenAI format."""
trimmed_messages = trim_messages(
messages,
token_counter=tiktoken_counter,
strategy="last",
max_tokens=45,
start_on="human",
end_on=("human", "tool"),
include_system=True,
)
openai_format_messages = convert_to_openai_messages(trimmed_messages)
return openai_format_messages
# Test
# messages = [SystemMessage(content="You are a helpful assistant."), HumanMessage(query)]
# openai_format_messages = trim_messages_openai(messages) |