如何获取 pandas DataFrame的最后N行? [英] How to get the last N rows of a pandas DataFrame?

问题描述

我有pandas数据帧df1和df2(df1是vanila数据帧，df2由'STK_ID'和'RPT_Date'索引):

I have pandas dataframe df1 and df2 (df1 is vanila dataframe, df2 is indexed by 'STK_ID' & 'RPT_Date') :

>>> df1
    STK_ID  RPT_Date  TClose   sales  discount
0   000568  20060331    3.69   5.975       NaN
1   000568  20060630    9.14  10.143       NaN
2   000568  20060930    9.49  13.854       NaN
3   000568  20061231   15.84  19.262       NaN
4   000568  20070331   17.00   6.803       NaN
5   000568  20070630   26.31  12.940       NaN
6   000568  20070930   39.12  19.977       NaN
7   000568  20071231   45.94  29.269       NaN
8   000568  20080331   38.75  12.668       NaN
9   000568  20080630   30.09  21.102       NaN
10  000568  20080930   26.00  30.769       NaN

>>> df2
                 TClose   sales  discount  net_sales    cogs
STK_ID RPT_Date                                             
000568 20060331    3.69   5.975       NaN      5.975   2.591
       20060630    9.14  10.143       NaN     10.143   4.363
       20060930    9.49  13.854       NaN     13.854   5.901
       20061231   15.84  19.262       NaN     19.262   8.407
       20070331   17.00   6.803       NaN      6.803   2.815
       20070630   26.31  12.940       NaN     12.940   5.418
       20070930   39.12  19.977       NaN     19.977   8.452
       20071231   45.94  29.269       NaN     29.269  12.606
       20080331   38.75  12.668       NaN     12.668   3.958
       20080630   30.09  21.102       NaN     21.102   7.431

我可以通过以下方式获得df2的最后3行:

I can get the last 3 rows of df2 by:

>>> df2.ix[-3:]
                 TClose   sales  discount  net_sales    cogs
STK_ID RPT_Date                                             
000568 20071231   45.94  29.269       NaN     29.269  12.606
       20080331   38.75  12.668       NaN     12.668   3.958
       20080630   30.09  21.102       NaN     21.102   7.431

而df1.ix[-3:]给出所有行:

>>> df1.ix[-3:]
    STK_ID  RPT_Date  TClose   sales  discount
0   000568  20060331    3.69   5.975       NaN
1   000568  20060630    9.14  10.143       NaN
2   000568  20060930    9.49  13.854       NaN
3   000568  20061231   15.84  19.262       NaN
4   000568  20070331   17.00   6.803       NaN
5   000568  20070630   26.31  12.940       NaN
6   000568  20070930   39.12  19.977       NaN
7   000568  20071231   45.94  29.269       NaN
8   000568  20080331   38.75  12.668       NaN
9   000568  20080630   30.09  21.102       NaN
10  000568  20080930   26.00  30.769       NaN

为什么?如何获得df1的最后3行(无索引的数据帧)? 熊猫0.10.1

Why ? How to get the last 3 rows of df1 (dataframe without index) ? Pandas 0.10.1

推荐答案

别忘了DataFrame.tail！例如df1.tail(10)

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