1.ndim, shape, dtype, astype usage
1.ndim dimension of an array is returned, only to return a number, this number means that the dimension of the array
2.shape: it represents tuple dimension size. It returns a tuple
3.dtype: object array for explaining a data type. It returns the data type of the array
4.astype: data type conversion array
2.reshape () array is the array method, the role of the data is reorganized
3.