Table of Contents
Lesson 3.2: The Loop (Cycles)
Table of Contents1 The Scenario2 The Code3 Output (Randomized)4 Key Concept: Recursion Limit The most powerful feature of LangGraph is that it allows Cycles. You can draw an edge from Node B back to Node A. This creates a loop. The Scenario A “Coin Flip” game. The agent keeps flipping a coin until it gets
Lesson 3.1: The Router (Conditional Edges)
Table of Contents1 The Scenario2 The Code3 Output A standard edge (add_edge) is like a train track; the train must go there. A conditional edge (add_conditional_edges) is like a junction. The graph pauses, looks at the State, and decides which track to take. To implement this, we need a special Routing Function. This function doesn’t
Lesson 2.2 The Solution: Reducers
Table of Contents1 The Fixed Code1.1 What is the Annotated type?1.2 How LangGraph Uses It2 The Result3 Why is this Critical? (The Chatbot Use Case)4 Real-World Example: Chat State To fix the overwrite issue in lesson 1, we need to tell LangGraph: “When you receive new data for ‘topics’, do not replace the old data.
Lesson 2.1 The Problem: The "Overwrite" Bug
Table of Contents1 The Broken Code2 The Result Let’s look at what happens when two nodes try to write to the same field in the state using the method from Module 1. The Broken Code We want to collect a list of topics. Node 1 finds “AI”. Node 2 finds “Crypto”. The Result What happened
Lesson 1.2: The "Broken Telephone" (Why State Matters)
Table of Contents1 The Code (The Mistake)2 The Result3 The fix The most important concept in Module 1 is the State Schema. In Python, you can pass any variable to any function. In LangGraph, the State is strict. If you try to pass data that isn’t defined in your TypedDict, it vanishes (or causes errors