我有2个数据框，它看起来像这样：
DF1：
Product, Region, ProductScore
AAA, R1,100
AAA, R2,100
BBB, R2,200
BBB, R3,200
DF2：
Region, RegionScore
R1,1
R2,2
我如何让这两个加入1个数据帧，结果应如下所示：
Product, Region, ProductScore, RegionScore
AAA, R1,100,1
AAA, R2,100,2
BBB, R2,200,2
非常感谢！
编辑1：
我用了df.merge（df_new）
得到此错误消息：
File "C:\Python34\lib\site-packages\pandas\core\frame.py", line 4071, in merge
suffixes=suffixes, copy=copy)
File "C:\Python34\lib\site-packages\pandas\tools\merge.py", line 37, in merge
copy=copy)
File "C:\Python34\lib\site-packages\pandas\tools\merge.py", line 183, in __init__
self.join_names) = self._get_merge_keys()
File "C:\Python34\lib\site-packages\pandas\tools\merge.py", line 318, in _get_merge_keys
self._validate_specification()
File "C:\Python34\lib\site-packages\pandas\tools\merge.py", line 409, in _validate_specification
if not self.right.columns.is_unique:
AttributeError: 'list' object has no attribute 'is_unique'
编辑2：
我意识到我的df_new是一个数据系列（通过使用groupby创建）而不是数据帧。现在我已经将其转换为数据框，这是信息：
打印（df.info（））
Int64Index：1111个条目，0到1110
数据列（共8列）：
产品1111非空对象
reviewuserId 1111非空对象
reviewprofileName 1111非空对象
评论881非空float64
reviewscore 1111非null float64
审阅时间1111非null int64
总结1111非空对象
reviewtext 1111非空对象
dtypes：float64（2），int64（1），object（5）
内存使用量：56.4+ KB
没有
print(df_new_2.info())
<class 'pandas.core.frame.DataFrame'>
Index: 1089 entries, A100Y8WSLFJN7Q to AZWBQPQN96SS6
Data columns (total 1 columns):
reviewelpfulnessbyuserid 864 non-null float64
dtypes: float64(1)
memory usage: 12.8+ KB
None
print(df.head())
product reviewuserId reviewprofileName \
0 B003AI2VGA A141HP4LYPWMSR Brian E. Erland "Rainbow Sphinx"
1 B003AI2VGA A328S9RN3U5M68 Grady Harp
2 B003AI2VGA A1I7QGUDP043DG Chrissy K. McVay "Writer"
3 B003AI2VGA A1M5405JH9THP9 golgotha.gov
4 B003AI2VGA ATXL536YX71TR KerrLines ""MoviesMusicTheatre""
reviewelpfulness reviewscore reviewtime \
0 1.0 3 1182729600
1 1.0 3 1181952000
2 0.8 5 1164844800
3 1.0 3 1197158400
4 1.0 3 1188345600
reviewsummary \
0 There Is So Much Darkness Now ~ Come For The M...
1 Worthwhile and Important Story Hampered by Poo...
2 This movie needed to be made.
3 distantly based on a real tragedy
4 What's going on down in Juarez and shining a l...
reviewtext
0 Synopsis: On the daily trek from Juarez Mexico...
1 THE VIRGIN OF JUAREZ is based on true events s...
2 The scenes in this film can be very disquietin...
3 THE VIRGIN OF JUAREZ (2006)<br />directed by K...
4 Informationally this SHOWTIME original is esse...
print(df_new_2.head())
reviewelpfulnessbyuserid
reviewuserId
A100Y8WSLFJN7Q NaN
A103VZ3KDF2RT5 0.555556
A1041HQGJDKFG5 0.000000
A10FBJXMQPI0LL 0.333333
A10LIHFA4SSK3F 0.000000
现在错误味精看起来像这样：
File "pandas\hashtable.pyx", line 694, in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12245)
KeyError: 'reviewuserId'
打印这些信息后，我只需添加以下即可解决此问题：
df_new_2 = df_new.to_frame().reset_index() 最佳答案
您要的不是左合并，因为您用R3跳过了该行，您只想执行一个内部merge：
In [120]:
df.merge(df1)
Out[120]:
Product Region ProductScore RegionScore
0 AAA R1 100 1
1 AAA R2 100 2
2 BBB R2 200 2
左合并将导致以下结果：
In [121]:
df.merge(df1, how='left')
Out[121]:
Product Region ProductScore RegionScore
0 AAA R1 100 1
1 AAA R2 100 2
2 BBB R2 200 2
3 BBB R3 200 NaN
关于python - 如何使用 Pandas 左联接，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/32777922/