sum()とsum(1)は何が違うのか？？：Python,NumPy

全部足すか列ごとに足すかの違いでした～

In [46]: import numpy as np

In [47]: A=np.array([[  2,4,6.],
    ...:  [  4,8,12.],
    ...:  [  6,12,18.]])

In [48]: A.sum()
Out[48]: 72.0

In [49]: A.sum(1)
Out[49]: array([ 12.,  24.,  36.])