Conditional Graph · Langgraph

Objectives ✅

Implement conditional logic to route the flow of data to different nodes.
Use Start and End nodes, to manage entry and exit points explicitly.
Design multiple nodes to perform different operations(addition, subtraction).
Create a router node to handel decision -making and control graph flow

python

from typing import TypedDict
from langgraph.graph import StateGraph, START, END

class AgentState(TypedDict):
    number1: int
    operation: str
    number2: int
    finalNumber: int

python

def adder(state: AgentState) -> AgentState:
    """This node adds two numbers together."""
    state['finalNumber'] = state['number1'] + state['number2']
    return state

def subtractor(state: AgentState) -> AgentState:
    """This node subtracts two numbers."""
    state["finalNumber"] = state["number1"] - state["number2"]
    return state

def decide_next_node(state: AgentState) -> AgentState:
    """This node will select the next node of the graph"""
    if state["operation"] == "+":
        return "addition_operation"
    elif state["operation"] == "-":
        return "subtraction_operation"

python

graph = StateGraph(AgentState)

graph.add_node("add_node", adder)
graph.add_node("subtract_node", subtractor)
graph.add_node("router", lambda state: state) # Pass-through Node

graph.add_edge(START, "router")
graph.add_conditional_edges(
    "router",
    decide_next_node,
    {
        # Edge: Node
        "addition_operation": "add_node",
        "subtraction_operation": "subtract_node"
    }
)
graph.add_edge("add_node", END)

app = graph.compile()

python

result = app.invoke({"number1": 15, "number2": 30, "operation": "+"})

print(result["finalNumber"])

powershell

OUTPUT:

'45'