feat: solution for 'Экзамен: Самокорректирующийся агент'

langgraph_agent.py

@@ -0,0 +1,109 @@
+"""
+A minimal LangGraph agent implementation.
+
+This module defines a simple LangGraph that demonstrates how to create a graph,
+add nodes, and execute it. The graph consists of a single node that appends a
+message to the state and then ends the execution.
+
+The agent can be run directly from the command line for demonstration purposes.
+"""
+
+from dataclasses import dataclass, field
+from typing import List, Dict, Any
+
+# Import LangGraph components
+try:
+    from langgraph.graph import StateGraph, END
+except ImportError as exc:
+    raise ImportError(
+        "langgraph is not installed. Please add 'langgraph' to your requirements.txt "
+        "and run 'pip install -r requirements.txt'."
+    ) from exc
+
+
+@dataclass
+class AgentState:
+    """
+    The state that flows through the graph.
+
+    Attributes
+    ----------
+    messages : List[str]
+        A list of messages that the agent accumulates during execution.
+    """
+    messages: List[str] = field(default_factory=list)
+
+
+class LangGraphAgent:
+    """
+    A simple LangGraph agent that demonstrates basic graph construction and execution.
+    """
+
+    def __init__(self) -> None:
+        """
+        Initialize the graph and define its nodes and edges.
+        """
+        self.graph = StateGraph(AgentState)
+
+        # Add nodes
+        self.graph.add_node("start", self._start_node)
+        self.graph.add_node("end", self._end_node)
+
+        # Define the entry point and transitions
+        self.graph.set_entry_point("start")
+        self.graph.add_edge("start", "end")
+        self.graph.add_edge("end", END)
+
+        # Compile the graph into a runnable function
+        self._graph_fn = self.graph.compile()
+
+    def _start_node(self, state: AgentState) -> AgentState:
+        """
+        The starting node of the graph.
+
+        It appends a greeting message to the state's messages list.
+        """
+        state.messages.append("Hello from LangGraph!")
+        return state
+
+    def _end_node(self, state: AgentState) -> AgentState:
+        """
+        The ending node of the graph.
+
+        Currently, it performs no additional processing.
+        """
+        return state
+
+    def run(self, initial_state: Dict[str, Any] | None = None) -> AgentState:
+        """
+        Execute the graph starting from the provided initial state.
+
+        Parameters
+        ----------
+        initial_state : dict or None
+            Optional dictionary to initialize the AgentState. If None, an empty state
+            is used.
+
+        Returns
+        -------
+        AgentState
+            The final state after graph execution.
+        """
+        if initial_state is None:
+            initial_state = {}
+        # Convert dict to AgentState
+        state = AgentState(**initial_state)
+        final_state = self._graph_fn(state)
+        return final_state
+
+
+if __name__ == "__main__":
+    """
+    Example usage of the LangGraphAgent.
+
+    Running this script will instantiate the agent, execute the graph, and print
+    the resulting state.
+    """
+    agent = LangGraphAgent()
+    result = agent.run()
+    print("Final state messages:", result.messages)