Initial commit: add LangGraph examples

2026-07-25 01:59:24 +08:00
commit e5d701a045
4 changed files with 567 additions and 0 deletions
--- a/basic_agent.py
+++ b/basic_agent.py
@@ -0,0 +1,115 @@
+"""
+Basic LangGraph Example - A simple conversational agent with state management.
+
+This demonstrates core LangGraph concepts:
+- State schemas
+- Nodes (functions that process state)
+- Edges (connections between nodes)
+- Conditional routing
+"""
+
+from typing import TypedDict, Literal, Annotated
+from langgraph.graph import StateGraph, START, END
+from langgraph.graph.message import add_messages
+
+
+# Define the state schema
+class State(TypedDict):
+    """State represents what flows through our graph."""
+    messages: Annotated[list, add_messages]
+    counter: int
+
+
+# Define node functions
+def greeting_node(state: State) -> dict:
+    """Process greeting messages."""
+    print("Processing greeting...")
+    return {"counter": state["counter"] + 1}
+
+
+def math_node(state: State) -> dict:
+    """Process math-related messages."""
+    print("Processing math request...")
+    return {"counter": state["counter"] + 1}
+
+
+def default_node(state: State) -> dict:
+    """Handle unknown/unrecognized messages."""
+    print("Handling general message...")
+    return {"counter": state["counter"] + 1}
+
+
+# Define the router function
+def route_message(state: State) -> Literal["greeting", "math", "default"]:
+    """Route to appropriate node based on message content."""
+    messages = state["messages"]
+    if not messages:
+        return "default"
+
+    last_message = messages[-1].lower() if isinstance(messages[-1], str) else str(messages[-1]).lower()
+
+    if any(word in last_message for word in ["hello", "hi", "hey", "greetings"]):
+        return "greeting"
+    elif any(word in last_message for word in ["add", "subtract", "multiply", "divide", "calculate"]):
+        return "math"
+    else:
+        return "default"
+
+
+# Build the graph
+def create_graph():
+    """Create and compile the LangGraph workflow."""
+
+    # Initialize the graph builder
+    builder = StateGraph(State)
+
+    # Add nodes
+    builder.add_node("greeting", greeting_node)
+    builder.add_node("math", math_node)
+    builder.add_node("default", default_node)
+
+    # Add edges with conditional routing
+    builder.add_conditional_edges(
+        START,
+        route_message,
+        {
+            "greeting": "greeting",
+            "math": "math",
+            "default": "default"
+        }
+    )
+
+    # All nodes lead to END (or could chain to other nodes)
+    builder.add_edge("greeting", END)
+    builder.add_edge("math", END)
+    builder.add_edge("default", END)
+
+    # Compile the graph
+    return builder.compile()
+
+
+def main():
+    """Run the basic LangGraph agent."""
+    graph = create_graph()
+
+    print("=== Basic LangGraph Agent ===")
+    print("Try messages like: 'hello', 'add 5 and 3', or anything else")
+    print()
+
+    # Test cases
+    test_messages = [
+        "Hello there!",
+        "Can you add 5 and 3?",
+        "What's the weather like?"
+    ]
+
+    for message in test_messages:
+        print(f"Input: {message}")
+        initial_state = {"messages": [message], "counter": 0}
+        result = graph.invoke(initial_state)
+        print(f"Output: Processed with counter = {result['counter']}")
+        print()
+
+
+if __name__ == "__main__":
+    main()