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my_agent/src/simple_agent/tools/math_tools.py

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+import ast
+from typing import Any
+from langchain_core.tools import tool
+@tool
+def calculator(expression: str) -> str:
+    """安全地计算数学表达式。支持 +, -, *, /, %, ** 和括号。"""
+    try:
+        parsed = ast.parse(expression, mode="eval")
+        allowed_nodes = (
+            ast.Expression, ast.BinOp, ast.UnaryOp, ast.Constant,
+            ast.Add, ast.Sub, ast.Mult, ast.Div, ast.Mod, ast.Pow,
+            ast.USub, ast.UAdd, ast.Load,
+        )
+        for node in ast.walk(parsed):
+            if not isinstance(node, allowed_nodes):
+                return f"错误：表达式 '{expression}' 包含不支持的运算或符号，请只用加减乘除、括号和幂运算。"
+        result = eval(compile(parsed, "<calculator>", "eval"), {"__builtins__": {}}, {})
+        return str(result)
+    except Exception as e:
+        return f"计算出错: {str(e)}"
+