python - 从其他数据集映射数据。 python Pandas

Question

所以我得到了 2 个数据集，df1 有所有水果的颜色，而 df2 没有。如何根据水果名称，根据 d1 的颜色数据映射 df2 的颜色值？

               df1                                  df2
Name               Color             Name              Color
Apple              Red               Orange            Na
Orange             Orange            Coconut           Na
Pear               Pear              Pear              Na
Pear               Pear              Strawberries      Na
Papaya             Papaya            Banana            Na
Watermelon         Watermelon        Papaya            Na
               "                  "                 "                 "

Answer 1

我认为你可以使用map ，但首先需要Series.drop_duplicates :

df2['Color'] = df2['Name'].map(df1.set_index('Name')['Color'].drop_duplicates())
print (df2)
           Name   Color
0        Orange  Orange
1       Coconut     NaN
2          Pear    Pear
3  Strawberries     NaN
4        Banana     NaN
5        Papaya  Papaya

另一个解决方案 merge与 DataFrame.drop_duplicates和 DataFrame.drop :

df2 = pd.merge(df2.drop('Color', axis=1),df1.drop_duplicates(), how='left')
print (df2)
           Name   Color
0        Orange  Orange
1       Coconut     NaN
2          Pear    Pear
3  Strawberries     NaN
4        Banana     NaN
5        Papaya  Papaya