定義一個函數“lookup_key(d, k)”用於從dictionary “d”中找尋key “k”︒請用try和except在找不到“k”時回報問題；用else處理找到“k”時print出k對應的value；用finally處理最終print出“lookup finish”︒

你可以定义一个名为`lookup_key`的函数，它接受两个参数：一个字典`d`和一个键`k`。下面是一个Python函数的实现，符合您给出的要求：

def lookup_key(d, k):
    try:
        value = d[k]
        print(f"Key '{k}' maps to value: {value}")
    except KeyError:
        print(f"Error: Key '{k}' not found in the dictionary.")
    else:
        pass  # No need for an explicit 'pass', as printing happens inside the try block
    finally:
        print("Lookup finished.")

# 示例用法
my_dict = {"name": "John", "age": 30}
lookup_key(my_dict, "name")  # Will print the value associated with key "name"
lookup_key(my_dict, "country")  # Will print "Error: Key 'country' not found in the dictionary."

在这个函数中，我们首先尝试从字典中获取给定的键。如果键存在，它的值会被打印出来。如果键不存在，则会引发`KeyError`异常，此时我们会捕获这个异常并输出错误信息。无论是否发生异常，最后都会执行`finally`块里的内容，即打印"Lookup finished."。