学习的过程中，遇到了asmatrix的用法，看了一下官方文档，明白了。

numpy.asmatrix

numpy.asmatrix(data, dtype=None)[source]

Interpret the input as a matrix.

Unlike matrix, asmatrix does not make a copy if the input is already a matrix or an ndarray. Equivalent to matrix(data, copy=False).

Parameters:	data : array_like Input data. dtype : data-type Data-type of the output matrix.
Returns:	mat : matrix data interpreted as a matrix.

Examples

>>> x = np.array([[1, 2], [3, 4]])

>>> m = np.asmatrix(x)

>>> x[0,0] = 5

>>> m

matrix([[5, 2],

        [3, 4]])