在Python字典中查找特定值的最有效方法是什么？

def find_key_by_value(dictionary, target_value):
    for key, value in dictionary.items():
        if value == target_value:
            return key
    return None

# 示例字典
my_dict = {"a": 1, "b": 2, "c": 3, "d": 2}

# 查找值为2的键
result = find_key_by_value(my_dict, 2)
print(result)  # 输出: b