reshape函数python python.reshape

使用数组的reshape方法，可以创建一个改变了尺寸的新数组，原数组的shape保持不变； 

>>> a = np.array([1, 2, 3, 4]);b = np.array((5, 6, 7, 8));c = np.array([[1, 2, 3, 4],[4, 5, 6, 7], [7, 8, 9, 10]])
>>> b
array([5, 6, 7, 8])
>>> c
array([[ 1,  2,  3,  4],
       [ 4,  5,  6,  7],
       [ 7,  8,  9, 10]])
>>> c.dtype
dtype('int32')
>>> d = a.reshape((2,2))
>>> d
array([[1, 2],
       [3, 4]])
>>> d = a.reshape((1,2))
Traceback (most recent call last):
  File "<pyshell#27>", line 1, in <module>
    d = a.reshape((1,2))
ValueError: total size of new array must be unchanged
>>> d = a.reshape((1,-1))
>>> d
array([[1, 2, 3, 4]])
>>> d = a.reshape((-1,1))
>>> d
array([[1],
       [2],
       [3],
       [4]])

注意:a.reshape((1,-1))和a.reshape((1,2))和a.reshape((-1,1))