python - pandas - 合并两个数据框覆盖并指定要保留的列

Question

我正在尝试合并到 panda 数据帧，尽管我想要的实际上可能不是合并。

我在两个匹配的框架中有两列，其中一列共享可用于连接的唯一值。另一列有一个空字段和一个填充字段。

我想在匹配唯一字段时覆盖空字段，但只保留被覆盖的列，我不希望第二个 DataFrame 中的其余列。

希望下面能解释得更深入一些

>>> animals = [{"animal" : "dog", "name" : "freddy", "food" : ""},{"animal" : "cat", "name" : "dexter", "food" : ""},{"animal" : "dog", "name" : "lou lou", "food" : ""}]
>>> foods = [{"name" : "freddy", "food" : "dog mix", "brand" : "doggys dog"},{"name" : "dexter", "food" : "fussy cat mix", "brand" : "fish fishy"},{"name" : "lou lou", "food" : "bones", "brand" : "i was a cow"}]
>>> a_pd = pd.DataFrame(animals)
>>> a_pd
  animal food     name
0    dog        freddy
1    cat        dexter
2    dog       lou lou
>>> f_pd = pd.DataFrame(foods)
>>> f_pd
         brand           food     name
0   doggys dog        dog mix   freddy
1   fish fishy  fussy cat mix   dexter
2  i was a cow          bones  lou lou
>>>
>>>
>>> animal_data = a_pd.merge(f_pd, on='name', how='left')
>>> animal_data
  animal food_x     name        brand         food_y
0    dog          freddy   doggys dog        dog mix
1    cat          dexter   fish fishy  fussy cat mix
2    dog         lou lou  i was a cow          bones
>>>

我应该只吃食物，我不想要品牌(还要注意这是样本数据，实时数据有更多的列

想要的结果

>>> animal_data
  animal        name            food
0    dog      freddy         dog mix
1    cat      dexter   fussy cat mix
2    dog     lou lou           bones

Answer 1

使用:

animal_data = a_pd.merge(f_pd, on='name', how='left', suffixes=('_x','')).drop('food_x', axis=1)

输出:

  animal     name        brand           food
0    dog   freddy   doggys dog        dog mix
1    cat   dexter   fish fishy  fussy cat mix
2    dog  lou lou  i was a cow          bones

或者

a_pd[['animal','name']].merge(f_pd, how='left')

输出:

  animal     name        brand           food
0    dog   freddy   doggys dog        dog mix
1    cat   dexter   fish fishy  fussy cat mix
2    dog  lou lou  i was a cow          bones