pandas groupby基本用法

df = pd.DataFrame({'Animal' : ['Falcon', 'Falcon',
                               'Parrot', 'Parrot'],
                    'Max Speed' : [380., 370., 24., 26.]})

df.groupby(['Animal']).mean()

        Max Speed
Animal           
Falcon      375.0
Parrot       25.0

df.groupby(['Animal']).std()

        Max Speed
Animal           
Falcon   7.071068
Parrot   1.414214

df = pd.DataFrame({'A': [1, 1, 2, 2],
                   'B': [1, 2, 3, 4],
                   'C': np.random.randn(4)})
df.groupby(['A','B']).agg({'C':'last'})

            C
A B          
1 1 -0.409032
  2 -0.577949
2 3  2.700646
  4 -0.336110