数组操作符

print(x + y) # elementwise addition     [1 2 3] + [4 5 6] = [5  7  9]
print(x - y) # elementwise subtraction  [1 2 3] - [4 5 6] = [-3 -3 -3]

[5 7 9]
[-3 -3 -3]

print(x * y) # elementwise multiplication  [1 2 3] * [4 5 6] = [4  10  18]
print(x / y) # elementwise divison         [1 2 3] / [4 5 6] = [0.25  0.4  0.5]

[ 4 10 18]
[ 0.25  0.4   0.5 ]

print(x**2) # elementwise power  [1 2 3] ^2 =  [1 4 9]

[1 4 9]

x.dot(y) # dot product  1*4 + 2*5 + 3*6

32

z = np.array([y, y**2])
print(len(z)) # number of rows of array

2

z = np.array([y, y**2])
z

array([[ 4,  5,  6],
       [16, 25, 36]])

z.shape

(2, 3)

z.T

array([[ 4, 16],
       [ 5, 25],
       [ 6, 36]])

z.T.shape

(3, 2)

z.dtype

dtype('int64')

z = z.astype('f')
z.dtype

dtype('float32')