Now that our graph has logic (Module 3) and short-term memory (Module 2), we face a new problem: Long-term Memory. If you restart your script, the Python dictionary (State) is destroyed. The bot forgets who you are. To build a real application (like ChatGPT), you need to save the state to a database and reload … Read more
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 “Heads”. The Code Output (Randomized) Key Concept: Recursion Limit If you ran this … Read more
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 update the state; it simply returns the name … Read more
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. Add it to the old data.” We do this using a Reducer. In Python, the operator.add function adds two lists together ([‘a’] + [‘b’] = [‘a’, ‘b’]). We can … Read more
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 to “AI”? It was deleted. When Node B … Read more
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 depending on validation). Let’s see what happens when we try to … Read more