How get the NaN (missing values) during column sum of a Data frame in python?



I have created a Data frame in Ipython notebook in which there are some missing values and used it for the calculation of column sum of a Data frame but I am not getting any missing value in the result.I want to know how to get the missing value in the column sum of a Data frame.

df = DataFrame([[1.4, np.nan], [7.1, -4.5],
.....: [np.nan, np.nan], [0.75, -1.3]],
.....: index=['a', 'b', 'c', 'd'],
.....: columns=['one', 'two'])
one two
a 1.40 NaN
b 7.10 -4.5
c NaN NaN
d 0.75 -1.3

one 9.25
two -5.80



When summing data, NA (missing) values will be treated as zero.If the data are all NA, the result will be NA. Methods like cumsum and cumprod ignore NA values, but preserve them in the resulting arrays.

Hope this helps!