1In [152]: import numpy as np
2In [153]: import pandas as pd
3# to return the row and column indices where the value in NaN
4In [154]: np.where(pd.isnull(df))
5Out[154]: (array([2, 5, 6, 6, 7, 7]), array([7, 7, 6, 7, 6, 7]))
6
7In [155]: df.iloc[2,7]
8Out[155]: nan
9
10In [160]: [df.iloc[i,j] for i,j in zip(*np.where(pd.isnull(df)))]
11Out[160]: [nan, nan, nan, nan, nan, nan]