python - 将值从一个数据帧插入/替换/合并到另一个数据帧

Question

我有两个这样的数据框:

df1 = pd.DataFrame({'ID1':['A','B','C','D','E','F'],
                    'ID2':['0','10','80','0','0','0']})
df2 = pd.DataFrame({'ID1':['A','D','E','F'],
                    'ID2':['50','30','90','50'],
                    'aa':['1','2','3','4']})

我想插入ID2在df2进入ID2在df1 ，同时插入aa进入df1根据ID1获取像这样的新数据框:

df_result = pd.DataFrame({'ID1':['A','B','C','D','E','F'],
                       'ID2':['50','10','80','30','90','50'],
                         'aa':['1','NaN','NaN','2','3','4']})

我尝试过使用合并，但没有成功。

Answer 1

您可以使用combine_first将索引设置为 ID1 后在 DataFrame 上:

(df2.set_index('ID1')  # values of df2 have priority in case of overlap
    .combine_first(df1.set_index('ID1')) # add missing values from df1
    .reset_index()     # reset ID1 as column
)

输出:

  ID1 ID2   aa
0   A  50    1
1   B  10  NaN
2   C  80  NaN
3   D  30    2
4   E  90    3
5   F  50    4