[Solved] Given this code snippet using streaming:from langchain.callbacks.base import BaseCallbackHandler class PrintHandler(BaseCallbackHandler): def on_llm_new_token(self, token: str, **kwargs):... | LangChain

LangChain - Production Deployment

Given this code snippet using streaming:

from langchain.callbacks.base import BaseCallbackHandler

class PrintHandler(BaseCallbackHandler):
    def on_llm_new_token(self, token: str, **kwargs):
        print(token, end='')

handler = PrintHandler()
llm = OpenAI(streaming=True, callbacks=[handler])
llm('Hello')

What will be the output behavior?

ATokens print one by one immediately as they arrive.

BNothing prints until the full response is ready.

CAn error occurs because on_llm_new_token is missing.

DTokens print only after the entire response finishes.

Step-by-Step Solution

Solution:

Step 1: Understand on_llm_new_token callback
This method is called for each new token during streaming.
Step 2: Analyze print behavior
Printing tokens with end='' outputs tokens immediately without newline.
Final Answer:
Tokens print one by one immediately as they arrive. -> Option A
Quick Check:
Streaming with on_llm_new_token prints tokens live [OK]

Quick Trick: on_llm_new_token prints tokens as they stream in [OK]

Common Mistakes:

MISTAKES

Thinking output waits for full response
Assuming missing callback causes error
Confusing token printing timing

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More LangChain Quizzes

Given this code snippet using streaming:

Step 1: Understand on_llm_new_token callback

Step 2: Analyze print behavior

Final Answer:

Quick Check:

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