LangChain Expression Language - The ONLY video you need to TRULY understand LCEL

In this video, we'll do a deep dive into the LangChain Expression Language-the backbone of LangChain. This is the only video you'll need to really understand the ins and outs of LCEL and its Runnable Interface.
Code: github.com/Coding-Crashkurse/...
Timestamps:
0:00 - Intro
0:37 - Basic Chain and invoke method
3:06 - The magic of the pipe operator
8:11 - RunnablePassThrough
9:02 - RunnableLambda
10:03 - RunnableParallel
13:00 - More complicated chains
18:35 - Real world Chain - easy!
#langchain #LCEL

[@pratiknarendraraut6889]

Best teacher on CZcams , get this man on million subs asap.

[@ramishelh9998]

One of the best tutorials on LCEL. Thanks a lot!

[@codingcrashcourses8533]

Thank you very much

[@efneogearbox]

This is one of the best LCEL tutorials, not directly copying examples from LangChain website. Thank you!

[@eloiseidlitz7062]

Purely helpful ! I love it ! Big thank to you !

[@codingcrashcourses8533]

Thank you for your comment

[@mr.daniish]

Pure knowledge bomb!

[@matuskokoska312]

exctremely helpful video, thank you very much

[@mateusztylec215]

This is just great!

[@codingcrashcourses8533]

Thank you :)

[@user-sj1tp5mg6v]

It's awesome video!!! I finally figured out how it works! Thank you very much! ❤❤❤❤
And I absolutely agree with idea that this great video should be in their shitty docs

[@codingcrashcourses8533]

thank you for that great feedback

[@thunken]

@@codingcrashcourses8533 yeah their docs need attention; great vid

[@deadlooop]

Gave you the the * in git repo, and subscribed as well 👍

[@SashaBaych]

Finally!

[@yazanrisheh5127]

This definitely helped me understand more about LCEL. Thank you so much.
Just to make sure I understood what you explained in the video, runnablepassthrough is simply taking any input variable and it keeps it as it is to pass it to another runnable right? For example if I wanted to implement memory in my RAG application, I would create a function and where the input of it is from the runnablepassthrough and I pass that into a runnablelambda. If I had another function, I'd do the same and pass it inside runnablelamdba and finally to construct the entire chain, I connect them all to a runnable parralel. Is this right?
Also, sometimes I see "itemgetter" on langchain docs. Could you explain what that is

[@codingcrashcourses8533]

Yes. For Memory pass the memory through the RunnablePassthrough and don´t change it until you pass it to the model.
Itemgetter does the exact same as lamdba x: x[key]. Use that when you have dictionaries as objects.

[@yazanrisheh5127]

@@codingcrashcourses8533 Thank you so much!

[@farhanafridi8694]

❤❤

[@pnhbs392]

around 19 min, `{"context": retriever | format _docs, "question": RunnablePassthrough ()}` is the first item in the chain ... how exactly does that get coerced to a RunnableParallel? What does the coercing and when is it done? In Python, `__or__` is called on the item to the left of the operator, which here is a dictionary ...

[@codingcrashcourses8533]

LCEL does some kind of magic and interpretes this as RunnableParallel. How be honest, I don´t really know how

[@Lowlightu]

Amazing video!
Interestingly the result of the RAG was Tuna instead of "thuna", any idea why it didn't use the word from your documents and supposedly used its own knowledge.

[@codingcrashcourses8533]

Interesting point. I guess the llm just corrected the Spelling mistake

[@Kube4x]

How would it work if I had more than one input var in the prompt. For example, my prompt has {height} and {weight} how do I pass both values with runnable ?

[@codingcrashcourses8533]

Input={weight: 1, weight: 1}

[@jacehua7334]

Really great video so I'm guessing you can actually pass the metadata the same way that you do at the end so the LLM can consider the metadata as well?

[@codingcrashcourses8533]

The metadata is not for the LLM, the metadata is for you. Retrievers can use them to filter or so, but you don´t pass them to the LLM

[@jacehua7334]

@@codingcrashcourses8533 let’s say I want to do a recommendation system of some sort. Besides considering the text embeddings how might I also include the metadata as a consideration. I’ve seen people do self querying but kind of interested if this can be put in as well into the prompt.

[@codingcrashcourses8533]

@@jacehua7334 Well to be honest, I don´t see any value in doing that, but you can of cause preprocess your documents and just append the metadata as string to the content and tell the LLM to take it into consideration for whatever you want. But I think it´s a bad idea to pass it to the LLM. Do whatever you want before, but don´t pass it to the LLM

[@farhanafridi8694]

Is their any way i can include memory in the code you provided at the last?
I am encountering errors while doing it.

[@codingcrashcourses8533]

What did you try?

[@nintendo2000]

what vs code extension are you using to run notebooks?

[@codingcrashcourses8533]

None, vscode has that built-in

[@abhinavmane60]

Hey I am building a bot for a call centre but I want the bot to do a credential check first like confirm the name how do I achieve that please respond.

[@codingcrashcourses8533]

You need some kind of routing mechanism to detect this. You can watch my "routing" video on my channel to take the ideas from there.

[@abhinavmane60]

@@codingcrashcourses8533 Oh okay thanks see you there

[@user-dk8dm8db8t]

Can you share the notebook? It'd be of great help!

[@codingcrashcourses8533]

sorry - totally forgot to include that. Updated the description. Thank you for pointing it out

[@user-dk8dm8db8t]

@@codingcrashcourses8533 No prob!

[@user-dk8dm8db8t]

@@codingcrashcourses8533 Thanks!

[@ericmagalhaes]

If possible I would give 1k likes! that solved hours of studying!

[@codingcrashcourses8533]

Thank you for that comment. Really appreciate that :)

[@yazanrisheh5127]

first

[@kacperwodarczyk9349]

in their shitty documentation should be a links to your videos

[@codingcrashcourses8533]

haha thank you :)

[@fraternitas5117]

LCEL is a huge mistake to invest in.

[@codingcrashcourses8533]

Why?

[@fraternitas5117]

@@codingcrashcourses8533 because it is a DSL and not a general purpose programming language it forces vendor lockin.