使用字符串定义Numpy数组切片(Using a string to define Numpy array slice)

 首先，类名不能以整数开头。 所以重命名它们： 
 
 class A
 {
    public:
        int stuff;
    private:
        class B 
        {
        public:
            int stuffer;
        private:
            int x;
        };
  };
 
 其次，由于嵌套类B在私有部分中，因此您无法从类A的范围之外访问它。 B仅可由A访问。 声明类型B的对象的语法是B bObj; 在A的范围内。 
 
 现在你应该先尝试自己，然后再提出更多问题！ 
 
 
 至于你的编辑（增加的问题）：它没有编译， 因为当编译器看到B temp ，它还没有看到B的定义，这就是为什么它说B没有被声明！ 
 
 修复非常简单。 在使用它之前声明B ，如下所示： 
 
class A
{
private:
        class B 
        {
        public:
            int stuffer;
        private:
            int x;
        };
    public:
        int stuff;
        void helper(B temp, int d);

 }; //<--- this is also fixed. your code has 'colon', instead semi-colon!
 
 同时阅读课程结束时的评论！ 

First of all, class name cannot start with integer. So renaming them:
 
 class A
 {
    public:
        int stuff;
    private:
        class B 
        {
        public:
            int stuffer;
        private:
            int x;
        };
  };
 
Second, since the nested class B is in the private section, so you cannot access it from outside the scope of class A. B is accessible to A only. And the syntax of declaring an object of type B would be B bObj; in the scope of A.
 
Now you should try yourself first, before asking futher questions!
 
 
As for your edit (the added question): it's not compiling because by the time the compiler sees B temp, it has not yet seen the definition of B, that is why it says B is not declared!
 
The fix is very simple. Declare B before it's used, something like this:
 
class A
{
private:
        class B 
        {
        public:
            int stuffer;
        private:
            int x;
        };
    public:
        int stuff;
        void helper(B temp, int d);

 }; //<--- this is also fixed. your code has 'colon', instead semi-colon!
 
Also read the comment at the end of the class!