How can you combine RunnablePassthrough and RunnableLambda to create a runnable that first passes input unchanged, then doubles it?

hard📝 Application Q9 of 15

LangChain - Chains and LCEL

How can you combine RunnablePassthrough and RunnableLambda to create a runnable that first passes input unchanged, then doubles it?

AUse RunnableLambda(lambda x: x * 2) only

BChain RunnablePassthrough then RunnableLambda(lambda x: x * 2)

CChain RunnableLambda(lambda x: x * 2) then RunnablePassthrough

DUse RunnablePassthrough only

Step-by-Step Solution

Solution:

Step 1: Understand chaining runnables
Chaining means running one runnable after another in order.
Step 2: Pass input unchanged first, then double
RunnablePassthrough passes input as is, then RunnableLambda doubles it.
Final Answer:
Chain RunnablePassthrough then RunnableLambda(lambda x: x * 2) -> Option B
Quick Check:
Passthrough then double = chain order matters [OK]

Quick Trick: Chain passthrough first, then lambda to transform [OK]

Common Mistakes:

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