开发环境： 1.MAC 10.12.4 2.python 2.7 错误信息：
data = pd.DataFrame({'activation_dt':[None, np.nan, 1]})
print (data)
activation_dt
0 NaN
1 NaN
2 1.0
data['filter'] = data['activation_dt'].isnull().astype(int)
print (data)
activation_dt filter
0 NaN 1
1 NaN 1
2 1.0 0
