Question

我有一个数据框：

In [73]: data = {'ID':[1234,1234,1234,1234,1235,1235,1236,1237,1237,1237,1237], 'Date':['1/4/2001','1/4/2001','6/1/2003','6/1/2003', '7/1/1998', '7/1/1998', '4/23/2005', '7/1/2005','7/1/2005','7/1/2005','7/1/2005'], 'CalcYr': [2018, 2019, 2018, 2019, 2007, 2008, 2018, 2016, 2017, 2018, 2019], 'Values':[0.1,0.1,0.2,0.3,0.3,0.4,0.6,0,0.1,0,0.2]}
In[74]: df = pd.DataFrame(data)

In [75]: df
Out[75]: 
      ID       Date  CalcYr  Values
0   1234   1/4/2001    2018     0.1
1   1234   1/4/2001    2019     0.1
2   1234   6/1/2003    2018     0.2
3   1234   6/1/2003    2019     0.3
4   1235   7/1/1998    2007     0.3
5   1235   7/1/1998    2008     0.4
6   1236  4/23/2005    2018     0.6
7   1237   7/1/2005    2016     0.0
8   1237   7/1/2005    2017     0.1
9   1237   7/1/2005    2018     0.0
10  1237   7/1/2005    2019     0.2

我想对ID和Date的相同值仅保留一行，其中CalcYr最大。例如，对于1234的ID和1/4/2001的Date，我只保留CalcYr为2019的行。结果将是：

         ID       Date  CalcYr  Values
    0   1234   1/4/2001    2019     0.1
    1   1234   6/1/2003    2019     0.3
    2   1235   7/1/1998    2008     0.4
    3   1236  4/23/2005    2018     0.6
    4   1237   7/1/2005    2019     0.2

Answer 1

使用：

df.groupby(['ID','Date'], as_index=False).max()

     ID       Date  CalcYr  Values
0  1234   1/4/2001    2019     0.1
1  1234   6/1/2003    2019     0.3
2  1235   7/1/1998    2008     0.4
3  1236  4/23/2005    2018     0.6
4  1237   7/1/2005    2019     0.2

熊猫数据框：仅获取某列值最大的行

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