我正试图将panda中的两个数据帧与大数据集合并，但这给我带来了一些问题。我将尝试用一个较小的例子来说明。
df1有一个设备列表和几个与设备相关的列：
Item ID Equipment Owner Status Location
1 Jackhammer James Active London
2 Cement Mixer Tim Active New York
3 Drill Sarah Active Paris
4 Ladder Luke Inactive Hong Kong
5 Winch Kojo Inactive Sydney
6 Circular Saw Alex Active Moscow
df2有一个使用设备的实例列表。这有一些类似于df1的列，但有些字段是NaN值，也记录了不在df1中的设备实例：
Item ID Equipment Owner Date Location
1 Jackhammer James 08/09/2020 London
1 Jackhammer James 08/10/2020 London
2 Cement Mixer NaN 29/02/2020 New York
3 Drill Sarah 11/02/2020 NaN
3 Drill Sarah 30/11/2020 NaN
3 Drill Sarah 21/12/2020 NaN
6 Circular Saw Alex 19/06/2020 Moscow
7 Hammer Ken 21/12/2020 Toronto
8 Sander Ezra 19/06/2020 Frankfurt
我希望最终得到的数据帧是：
Item ID Equipment Owner Status Date Location
1 Jackhammer James Active 08/09/2020 London
1 Jackhammer James Active 08/10/2020 London
2 Cement Mixer Tim Active 29/02/2020 New York
3 Drill Sarah Active 11/02/2020 Paris
3 Drill Sarah Active 30/11/2020 Paris
3 Drill Sarah Active 21/12/2020 Paris
4 Ladder Luke Inactive NaN Hong Kong
5 Winch Kojo Inactive NaN Sydney
6 Circular Saw Alex Active 19/06/2020 Moscow
7 Hammer Ken NaN 21/12/2020 Toronto
8 Sander Ezra NaN 19/06/2020 Frankfurt
相反，使用以下代码，我得到了重复的行，我认为这是因为NaN值：
data = pd.merge(df1, df2, how='outer', on=['Item ID'])
Item ID Equipment_x Equipment_y Owner_x Owner_y Status Date Location_x Location_y
1 Jackhammer NaN James James Active 08/09/2020 London London
1 Jackhammer NaN James James Active 08/10/2020 London London
2 Cement Mixer NaN Tim NaN Active 29/02/2020 New York New York
3 Drill NaN Sarah Sarah Active 11/02/2020 Paris NaN
3 Drill NaN Sarah Sarah Active 30/11/2020 Paris NaN
3 Drill NaN Sarah Sarah Active 21/12/2020 Paris NaN
4 Ladder NaN Luke NaN Inactive NaN Hong Kong Hong Kong
5 Winch NaN Kojo NaN Inactive NaN Sydney Sydney
6 Circular Saw NaN Alex NaN Active 19/06/2020 Moscow Moscow
7 NaN Hammer NaN Ken NaN 21/12/2020 NaN Toronto
8 NaN Sander NaN Ezra NaN 19/06/2020 NaN Frankfurt
理想情况下，我可以只删除_y列，但底部行中的数据意味着我将丢失重要信息。相反，我唯一能想到的是合并列，并强制panda比较每列中的值，并始终支持非NaN值。我不确定这是否可能？
合并列并强制panda比较每列中的值，并始终支持非NaN值。
这就是你的意思吗？
In [45]: data = pd.merge(df1, df2, how='outer', on=['Item ID', 'Equipment'])
In [46]: data['Location'] = data['Location_y'].fillna(data['Location_x'])
In [47]: data['Owner'] = data['Owner_y'].fillna(data['Owner_x'])
In [48]: data = data.drop(['Location_x', 'Location_y', 'Owner_x', 'Owner_y'], axis=1)
In [49]: data
Out[49]:
Item ID Equipment Status Date Location Owner
0 1 Jackhammer Active 08/09/2020 London James
1 1 Jackhammer Active 08/10/2020 London James
2 2 Cement Mixer Active 29/02/2020 New York Tim
3 3 Drill Active 11/02/2020 Paris Sarah
4 3 Drill Active 30/11/2020 Paris Sarah
5 3 Drill Active 21/12/2020 Paris Sarah
6 4 Ladder Inactive NaN Hong Kong Luke
7 5 Winch Inactive NaN Sydney Kojo
8 6 Circular Saw Active 19/06/2020 Moscow Alex
9 7 Hammer NaN 21/12/2020 Toronto Ken
10 8 Sander NaN 19/06/2020 Frankfurt Ezra
(据我所知(你真的不能在空列上合并。但是，如果值是NaN，则可以使用fillna获取该值并用其他值替换它。这不是一个非常优雅的解决方案，但它似乎至少解决了您的示例。
另请参阅pandas将两列与空值组合
一般情况下，您可以按如下方式执行：
# merge the two dataframes using a suffix that ideally does
# not appear in your data
suffix_string='_DF2'
data = pd.merge(df1, df2, how='outer', on=['Item_ID'], suffixes=('', suffix_string))
# now remove the duplicate columns by mergeing the content
# use the value of column + suffix_string if column is empty
columns_to_remove= list()
for col in df1.columns:
second_col= f'{col}{suffix_string}'
if second_col in data.columns:
data[col]= data[second_col].where(data[col].isna(), data[col])
columns_to_remove.append(second_col)
if columns_to_remove:
data.drop(columns=columns_to_remove, inplace=True)
data
结果是：
Item_ID Equipment Owner Status Location Date
0 1 Jackhammer James Active London 08/09/2020
1 1 Jackhammer James Active London 08/10/2020
2 2 Cement_Mixer Tim Active New_York 29/02/2020
3 3 Drill Sarah Active Paris 11/02/2020
4 3 Drill Sarah Active Paris 30/11/2020
5 3 Drill Sarah Active Paris 21/12/2020
6 4 Ladder Luke Inactive Hong_Kong NaN
7 5 Winch Kojo Inactive Sydney NaN
8 6 Circular_Saw Alex Active Moscow 19/06/2020
9 7 Hammer Ken NaN Toronto 21/12/2020
10 8 Sander Ezra NaN Frankfurt 19/06/2020
关于以下测试数据：
df1= pd.read_csv(io.StringIO("""Item_ID Equipment Owner Status Location
1 Jackhammer James Active London
2 Cement_Mixer Tim Active New_York
3 Drill Sarah Active Paris
4 Ladder Luke Inactive Hong_Kong
5 Winch Kojo Inactive Sydney
6 Circular_Saw Alex Active Moscow"""), sep='s+')
df2= pd.read_csv(io.StringIO("""Item_ID Equipment Owner Date Location
1 Jackhammer James 08/09/2020 London
1 Jackhammer James 08/10/2020 London
2 Cement_Mixer NaN 29/02/2020 New_York
3 Drill Sarah 11/02/2020 NaN
3 Drill Sarah 30/11/2020 NaN
3 Drill Sarah 21/12/2020 NaN
6 Circular_Saw Alex 19/06/2020 Moscow
7 Hammer Ken 21/12/2020 Toronto
8 Sander Ezra 19/06/2020 Frankfurt"""), sep='s+')