파이썬 기본함수 sum

Sum by rows and by columns:
>>> x = np.array([[1, 1], [2, 2]])
>>> x
array([[1, 1], [2, 2]])
>>> x.sum(axis=0) # columns (first dimension)
array([3, 3])
>>> x[:, 0].sum(), x[:, 1].sum()
(3, 3)
>>> x.sum(axis=1) # rows (second dimension)
array([2, 4])
>>> x[0, :].sum(), x[1, :].sum()
(2, 4)