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# like [StdoutCallbackHandler](https://github.com/hwchase17/langchain/blob/master/langchain/callbacks/stdout.py), but writes to a file When running experiments I have found myself wanting to log the outputs of my chains in a more lightweight way than using WandB tracing. This PR contributes a callback handler that writes to file what `StdoutCallbackHandler` would print. <!-- Thank you for contributing to LangChain! Your PR will appear in our release under the title you set. Please make sure it highlights your valuable contribution. Replace this with a description of the change, the issue it fixes (if applicable), and relevant context. List any dependencies required for this change. After you're done, someone will review your PR. They may suggest improvements. If no one reviews your PR within a few days, feel free to @-mention the same people again, as notifications can get lost. Finally, we'd love to show appreciation for your contribution - if you'd like us to shout you out on Twitter, please also include your handle! --> ## Example Notebook <!-- If you're adding a new integration, please include: 1. a test for the integration - favor unit tests that does not rely on network access. 2. an example notebook showing its use See contribution guidelines for more information on how to write tests, lint etc: https://github.com/hwchase17/langchain/blob/master/.github/CONTRIBUTING.md --> See the included `filecallbackhandler.ipynb` notebook for usage. Would it be better to include this notebook under `modules/callbacks` or under `integrations/`?  ## Who can review? Community members can review the PR once tests pass. Tag maintainers/contributors who might be interested: @agola11 <!-- For a quicker response, figure out the right person to tag with @ @hwchase17 - project lead Tracing / Callbacks - @agola11 Async - @agola11 DataLoaders - @eyurtsev Models - @hwchase17 - @agola11 Agents / Tools / Toolkits - @vowelparrot VectorStores / Retrievers / Memory - @dev2049 -->
76 lines
2.5 KiB
Python
76 lines
2.5 KiB
Python
"""Callback Handler that writes to a file."""
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from typing import Any, Dict, Optional, TextIO, cast
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from langchain.callbacks.base import BaseCallbackHandler
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from langchain.input import print_text
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from langchain.schema import AgentAction, AgentFinish
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class FileCallbackHandler(BaseCallbackHandler):
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"""Callback Handler that writes to a file."""
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def __init__(
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self, filename: str, mode: str = "a", color: Optional[str] = None
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) -> None:
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"""Initialize callback handler."""
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self.file = cast(TextIO, open(filename, mode))
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self.color = color
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def __del__(self) -> None:
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"""Destructor to cleanup when done."""
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self.file.close()
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def on_chain_start(
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self, serialized: Dict[str, Any], inputs: Dict[str, Any], **kwargs: Any
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) -> None:
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"""Print out that we are entering a chain."""
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class_name = serialized["name"]
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print_text(
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f"\n\n\033[1m> Entering new {class_name} chain...\033[0m",
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end="\n",
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file=self.file,
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)
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def on_chain_end(self, outputs: Dict[str, Any], **kwargs: Any) -> None:
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"""Print out that we finished a chain."""
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print_text("\n\033[1m> Finished chain.\033[0m", end="\n", file=self.file)
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def on_agent_action(
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self, action: AgentAction, color: Optional[str] = None, **kwargs: Any
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) -> Any:
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"""Run on agent action."""
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print_text(action.log, color=color if color else self.color, file=self.file)
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def on_tool_end(
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self,
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output: str,
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color: Optional[str] = None,
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observation_prefix: Optional[str] = None,
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llm_prefix: Optional[str] = None,
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**kwargs: Any,
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) -> None:
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"""If not the final action, print out observation."""
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if observation_prefix is not None:
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print_text(f"\n{observation_prefix}", file=self.file)
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print_text(output, color=color if color else self.color, file=self.file)
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if llm_prefix is not None:
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print_text(f"\n{llm_prefix}", file=self.file)
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def on_text(
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self,
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text: str,
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color: Optional[str] = None,
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end: str = "",
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**kwargs: Any,
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) -> None:
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"""Run when agent ends."""
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print_text(text, color=color if color else self.color, end=end, file=self.file)
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def on_agent_finish(
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self, finish: AgentFinish, color: Optional[str] = None, **kwargs: Any
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) -> None:
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"""Run on agent end."""
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print_text(
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finish.log, color=color if self.color else color, end="\n", file=self.file
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)
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