初始化
a = np.array([[1,2,3], [4,5,6]])
a.dtype
len(a) == a.shape[0]
np.zeros((2,3))
np.full((2, 3), 7)
np.eye(3,3)
np.ones((2,3))
np.empty((3,4))
随机矩阵
np.random.randint(0, 10, [2,3])
np.random.rand(2,3) # uniform
np.random.randn(2,3) # normal
np.random.uniform(0, 10, [2,3])
np.random.normal(0, 10, [2,3])
二维数组的索引
x = np.random.normal(0, 10, [4, 4])
x
x[1,2]
x[1, :]
x[:, 1]
x[:, 1:3]
x[-2:,-2:]
x[::2, 1::2]
