Hello World Graph · Langgraph

Objectives ✅

Understand and define the AgentState structure
Create simple node functions to process and update statte
Set up a basic LangGraph structure
Compile and invoke a LangGraph graph
Understand how data flows through a single-node in LangGraph

python

from typing import Dict, TypedDict

from langgraph.graph import StateGraph

python

class AgentState(TypedDict): # Our State Schema
    message: str

def greeting_node(state: AgentState) -> AgentState:
    '''Simple node that adds a greeting message to the state.'''

    state['message'] = "Hey " + state['message'] + ", how is your day going!"
    return state

python

graph = StateGraph(AgentState)

graph.add_node("greeter", greeting_node)

# START
graph.set_entry_point("greeter")

# END
graph.set_finish_point("greeter")

app = graph.compile()

python

result = app.invoke({"message": "Alice"})

result['message']

powershell

OUTPUT:

'Hey Alice, how is your day going!'