numpy array operation in python

Directly on the code.

a = np.random.randint(10, size=20).reshape(4,5)
b = np.random.randint(10, size=20).reshape(4,5)
a
>>>array([[9, 4, 9, 3, 8],
 	      [8, 1, 7, 0, 9],
      	  [0, 2, 8, 0, 4],
      	  [0, 7, 2, 6, 8]])
b
>>> array([[8, 9, 6, 3, 7],
           [6, 2, 0, 9, 4],
           [1, 9, 3, 8, 1],
           [8, 0, 5, 5, 7]])
a + b        #对应元素相加
>>>array([[17, 13, 15,  6, 15],
          [14,  3,  7,  9, 13],
          [ 1, 11, 11,  8,  5],
          [ 8,  7,  7, 11, 15]])
a - b         #对应元素相减
>>>array([[ 1, -5,  3,  0,  1],
          [ 2, -1,  7, -9,  5],
          [-1, -7,  5, -8,  3],
          [-8,  7, -3,  1,  1]])
a * b             #对应元素相乘
>>>array([[72, 36, 54,  9, 56],
          [48,  2,  0,  0, 36],
          [ 0, 18, 24,  0,  4],
          [ 0,  0, 10, 30, 56]])
a  /  b             #对应元素相除
>>>因为b中有元素为0 ，所以会报错