Display running cost in USD after each response

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "llm-chat"
-version = "0.2.0"
+version = "0.3.0"
 description = "A general CLI interface for large language models."
 authors = ["Paul Harrison <paul@harrison.sh>"]
 readme = "README.md"

src/llm_chat/chat.py

@@ -1,10 +1,11 @@
+from enum import StrEnum, auto
 from typing import Any, Protocol
 
 from openai import ChatCompletion
 from openai.openai_object import OpenAIObject
 
 from llm_chat.models import Conversation, Message, Role
-from llm_chat.settings import OpenAISettings
+from llm_chat.settings import Model, OpenAISettings
 
 INITIAL_SYSTEM_MESSAGES = [
     Message(
@@ -17,9 +18,20 @@ INITIAL_SYSTEM_MESSAGES = [
 ]
 
 
+class Token(StrEnum):
+    """Token type for the OpenAI chat."""
+
+    COMPLETION = auto()
+    PROMPT = auto()
+
+
 class ChatProtocol(Protocol):
     """Protocol for chat classes."""
 
+    @property
+    def cost(self) -> float:
+        """Get the cost of the conversation."""
+
     def send_message(self, message: str) -> str:
         """Send a message to the assistant."""
 
@@ -33,6 +45,17 @@ class Chat:
         context (optional): Context for the chat. Defaults to an empty list.
     """
 
+    _pricing: dict[Model, dict[Token, float]] = {
+        Model.GPT3: {
+            Token.COMPLETION: 0.002,
+            Token.PROMPT: 0.0015,
+        },
+        Model.GPT4: {
+            Token.COMPLETION: 0.06,
+            Token.PROMPT: 0.03,
+        },
+    }
+
     def __init__(
         self, settings: OpenAISettings | None = None, context: list[Message] = []
     ) -> None:
@@ -48,6 +71,11 @@ class Chat:
             self._settings = OpenAISettings()
         return self._settings
 
+    @property
+    def cost(self) -> float:
+        """Get the cost of the conversation."""
+        return self.conversation.cost
+
     def _make_request(self, message: str) -> dict[str, Any]:
         """Send a request to the OpenAI API.
 
@@ -66,15 +94,30 @@ class Chat:
         out: dict[str, Any] = response.to_dict()
         return out
 
-    def send_message(self, message: str) -> str:
+    def _calculate_cost(self, usage: dict[str, int]) -> None:
+        """Calculate the cost of a request."""
+        self.conversation.completion_tokens += usage["completion_tokens"]
+        self.conversation.prompt_tokens += usage["prompt_tokens"]
+        self.conversation.cost = round(
+            (self.conversation.completion_tokens / 1000)
+            * self._pricing[self.settings.model][Token.COMPLETION]
+            + (self.conversation.prompt_tokens / 1000)
+            * self._pricing[self.settings.model][Token.PROMPT],
+            6,
+        )
+
+    def send_message(self, prompt: str) -> str:
         """Send a message to the assistant.
 
         TODO: Add error handling.
         """
-        response = self._make_request(message)
-        message = response["choices"][0]["message"]["content"]
-        self.conversation.messages.append(Message(role=Role.ASSISTANT, content=message))
-        return message
+        request_response = self._make_request(prompt)
+        self._calculate_cost(request_response["usage"])
+        response: str = request_response["choices"][0]["message"]["content"]
+        self.conversation.messages.append(
+            Message(role=Role.ASSISTANT, content=response)
+        )
+        return response
 
 
 def get_chat(

src/llm_chat/cli.py

@@ -6,7 +6,7 @@ from prompt_toolkit import PromptSession
 from rich.console import Console
 from rich.markdown import Markdown
 
-from llm_chat.chat import get_chat
+from llm_chat.chat import ChatProtocol, get_chat
 from llm_chat.models import Message, Role
 from llm_chat.settings import DEFAULT_MODEL, DEFAULT_TEMPERATURE, Model, OpenAISettings
 
@@ -55,6 +55,11 @@ def load_context(path: Path) -> Message:
     return Message(role=Role.SYSTEM, content=content)
 
 
+def display_cost(console: Console, chat: ChatProtocol) -> None:
+    """Display the cost of the conversation so far."""
+    console.print(f"\n[bold green]Cost:[/bold green] ${chat.cost}\n")
+
+
 @app.command()
 def chat(
     api_key: Annotated[
@@ -107,7 +112,6 @@ def chat(
     context_messages = [load_context(path) for path in context]
 
     current_chat = get_chat(settings=settings, context=context_messages)
-    # current_chat = get_chat(settings=settings)
     console = get_console()
     session = get_session()
 
@@ -123,3 +127,4 @@ def chat(
         else:
             response = current_chat.send_message(prompt.strip())
             console.print(Markdown(response))
+            display_cost(console, current_chat)

src/llm_chat/models.py

@@ -27,6 +27,9 @@ class Conversation(BaseModel):
     """Conversation in the chat."""
 
     messages: list[Message]
+    completion_tokens: int = 0
+    prompt_tokens: int = 0
+    cost: float = 0.0
 
     model_config: ConfigDict = ConfigDict(  # type: ignore[misc]
         frozen=False,

tests/test_chat.py

@@ -1,14 +1,31 @@
 from unittest.mock import patch
 
+import pytest
+
 from llm_chat.chat import Chat
+from llm_chat.settings import Model, OpenAISettings
 
 
 def test_send_message() -> None:
     with patch("llm_chat.chat.Chat._make_request") as mock_make_request:
         mock_make_request.return_value = {
-            "choices": [{"message": {"content": "Hello!"}}]
+            "choices": [{"message": {"content": "Hello!"}}],
+            "usage": {"completion_tokens": 1, "prompt_tokens": 1},
         }
         conversation = Chat()
         response = conversation.send_message("Hello")
         assert isinstance(response, str)
         assert response == "Hello!"
+
+
+@pytest.mark.parametrize("model,cost", [(Model.GPT3, 0.000043), (Model.GPT4, 0.00105)])
+def test_calculate_cost(model: Model, cost: float) -> None:
+    with patch("llm_chat.chat.Chat._make_request") as mock_make_request:
+        mock_make_request.return_value = {
+            "choices": [{"message": {"content": "Hello!"}}],
+            "usage": {"completion_tokens": 10, "prompt_tokens": 15},
+        }
+        settings = OpenAISettings(model=model)
+        conversation = Chat(settings=settings)
+        _ = conversation.send_message("Hello")
+        assert conversation.cost == cost

tests/test_cli.py

@@ -29,6 +29,11 @@ class ChatFake:
     def _set_args(self, **kwargs: Any) -> None:
         self.args = kwargs
 
+    @property
+    def cost(self) -> float:
+        """Get the cost of the conversation."""
+        return 0.0
+
     def send_message(self, message: str) -> str:
         """Echo the received message."""
         self.received_messages.append(message)