google--adk-python/contributing/samples/workflows/loop

ADK Workflow Loop Sample

Overview

This sample demonstrates how to create a feedback loop between different nodes in ADK Workflows.

It takes a user-provided topic and uses the generate_headline agent to write a headline. The evaluate_headline agent then grades the headline as either "tech-related" or "unrelated", providing feedback if it's unrelated. The route_headline function checks this grade. If the headline is "unrelated", the workflow loops back to the generate_headline agent, passing the feedback so it can try again. This process repeats until a "tech-related" headline is generated.

In ADK Workflows, loops allow for iterative refinement and evaluation by conditionally routing execution back to an earlier node in the sequence.

Sample Inputs

• flower

• quantum mechanics

• renewable energy

Graph

graph TD
    START --> process_input
    process_input --> generate_headline
    generate_headline --> evaluate_headline
    evaluate_headline --> route_headline
    route_headline -->|unrelated| generate_headline
    route_headline -->|tech-related| END[Loop ends]

How To

1. Define a node (like route_headline) that yields an Event with a specific route based on a condition:

   def route_headline(node_input: Feedback):
     return Event(route=node_input.grade)
   

2. In the Workflow edges definition, create a conditional edge that connects the routing node back to a previous node in the workflow, using a routing map dict:

   (route_headline, {"unrelated": generate_headline})
   

   This creates the cycle. If the route yielded by route_headline is "unrelated", execution jumps back to generate_headline.