np.zeros()
a = np.zeros([2,3])
[[0. 0. 0.]
[0. 0. 0.]]
np.arange()
b = np.arange(5) # [0 1 2 3 4]
np.sum()
print(np.sum(b)) # 10
np.random.randn()
c = np.random.randn(2,3)
[[ 0.55061619 0.18269379 -0.6651352 ]
[ 0.63310865 -0.10882661 0.33937084]]
print(c.shape) # (2, 3)
print(c.ndim) # 2
print((c.dtype)) # float64
