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Exercises — Week 1 — Branching state

Do these after reading Week 1. The “done when” is two inputs taking different paths. Return partial dicts. Use a list reducer.

import operator
from typing import Annotated, Literal, TypedDict
from langgraph.graph import END, START, StateGraph

1. Two paths

Build a CloudWave ticket graph: classify → route → docs or refund_queue. Keyword ifs are fine.

Checks:

  • "How do I rotate an API key?" ends with a docs-path label
  • "I want a refund" ends with a refund-path label and never ran the docs node (count a RUNS counter like the week-3 lesson, or a path field)

2. Reducer

State has log: Annotated[list[str], operator.add]. classify returns {"log": ["classified"]}; the branch node returns {"log": ["docs"]} or {"log": ["refund"]}.

Checks:

  • After a docs ticket, log is ["classified", "docs"] (both entries present)
  • You did not state["log"].append(...) as the only write

3. Partial updates

A node that only knows the decision returns {"decision": "docs"} and does not pass the rest of the state through by mutation.

Checks:

  • classify(...) returns a dict whose keys are a subset of the state schema
  • Two invokes do not share a list object (no leaked labels from ticket 1 into ticket 2)

Predict before you run

Does "I want a refund" ever enter the docs node? After a docs ticket, is log ["classified", "docs"] or did you .append in place?

Starter / TODO

import operator
from typing import Annotated, Literal, TypedDict
from langgraph.graph import END, START, StateGraph
# TODO: classify → route → docs OR refund_queue
# TODO: log: Annotated[list[str], operator.add]

Runnable command

python your_ticket_graph.py   # compile + invoke, no API key

Expected observation

Two inputs, two paths. Refund path never increments a docs counter. Partial updates return a subset of the state keys.

Self-check

Return partial dicts. Use a list reducer. Two invokes do not share a list object.