dateframe_loc.iloc.ix

import pandas as pd
df=pd.DataFrame({
    "a":[1,2,3],
    "b":[4,5,6],
    "c":[7,8,9]
})
   a  b  c
0  1  2  3
1  4  5  6
2  7  8  9

df1=df['a']      #<class 'pandas.core.series.Series'>

df2=df[['a','b']]   #<class 'pandas.core.frame.DataFrame'>
#series取值
df1.ix[0,'a']
#dateframe取值
df2.ix[0,'b']

loc:根据标签

print(df2.loc[0:2,'a':'b'])#根据标签

   a  b  
0  1  2  
1  4  5  
2  7  8  

iloc:根据索引

print(df2.iloc[0:2,0:2])#根据索引

   a  b  
0  1  2  
1  4  5