categorical[np.arange(n), y] = 1 IndexError: index 2 is out of bounds for axis 1 with size 2

我的错误的代码是：train_labels = np_utils.to_categorical(train_labels,num_classes = 3)

错误的原因：

IndexError: index 2 is out of bounds for axis 1 with size 2

错误的具体指向：

categorical[np.arange(n), y] = 1 

这是因为train_labels不是numpy.array的形式，需要把train_labels转化为numpy数组的形式