合并中的一列只保留一行中的所有值，而不是为每个matc保留新行

Question

我想合并两个panda数据帧：

df 1

City      | Attraction | X | Z | Y
Somewhere    Rainbows    1   2   3
Somewhere    Trees       4   4   4
Somewhere    Unicorns

df 2

City      | Other Column | Also another column
Somewhere   Something      Something else

通常这样做：

df2.merge(df1[['City', 'Attraction']], left_on='City', right_on='City. how='left']
    City      | Other Column | Also another column | Attraction
Somewhere   Something      Something else              Rainbows
Somewhere   Something      Something else              Trees
Somewhere   Something      Something else              Unicorns

然而，我想将联接的结果分组到逗号分隔的列表中(或者其他什么(：

City      | Other Column | Also another column  | Attraction
Somewhere   Something      Something else         Rainbows, Trees, Unicorns

Answer 1

groupby()和map:

df2['Attaction'] = df2['City'].map(df1.groupby('City').Attraction.agg(', '.join))