[Solved] What will be the output of this code?passthrough = RunnablePassthrough() lambda_runner = RunnableLambda(lambda x: x.upper()) result = lambda_runner.invoke(passthrough.invoke('hello')) print(result) | LangChain

LangChain - Chains and LCEL

What will be the output of this code?

passthrough = RunnablePassthrough()
lambda_runner = RunnableLambda(lambda x: x.upper())
result = lambda_runner.invoke(passthrough.invoke('hello'))
print(result)

A'HELLO'

B'hello'

CError: RunnablePassthrough cannot be invoked

D'Hello'

Step-by-Step Solution

Solution:

Step 1: Trace RunnablePassthrough output
Calling passthrough.invoke('hello') returns 'hello' unchanged.
Step 2: Apply RunnableLambda function
The lambda converts input to uppercase, so 'hello'.upper() returns 'HELLO'.
Final Answer:
'HELLO' -> Option A
Quick Check:
Passthrough returns input, lambda uppercases it = C [OK]

Quick Trick: Passthrough returns input, lambda transforms it [OK]

Common Mistakes:

Expecting passthrough to modify input
Confusing case conversion result
Assuming runtime error on invoke

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What will be the output of this code?

Step 1: Trace RunnablePassthrough output

Step 2: Apply RunnableLambda function

Final Answer:

Quick Check:

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