Project 17: Search Assistant Logger
AI Engineer
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Current Task
Objective
A BaseCallbackHandler hooks into a chain's lifecycle events — like on_llm_start — giving visibility into what's happening at every step.
Task: define a callback handler that logs when the LLM starts, and print its log after a run.
index.py
from langchain_core.callbacks import BaseCallbackHandler
class SearchLogger(BaseCallbackHandler):
def __init__(self):
self.events = []
def on_llm_start(self, serialized, prompts, **kwargs):
self.events.append("llm_start")
logger = SearchLogger()
logger.on_llm_start({}, ["best hiking boots"])
print(logger.events)
* Hint: Correct characters turn green, incorrect ones turn red.
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