Python,Pandas:データフレーム操作

In [11]: import pandas as pd

In [12]: import numpy as np

In [13]: df = pd.DataFrame(np.array([[1,1,1,1],[1,'A',1,'B'],[1,'A',1,'B'],[1,1,1,'B']]), columns=['C1','C2','C3','C4'])

In [14]: df[df['C2']=='A'][['C2','C4']]
Out[14]: 
  C2 C4
1  A  B
2  A  B