Python / Pandas - KeyError 合并数据帧
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Python / Pandas - KeyError merging dataframes
提问by abutremutante
I have two dataframes I'm trying to merge:
我有两个要合并的数据框：
target:
version city_id code
id
4 2 4 5736201000175
26 2 3 8290265000183
27 3 3 9529184000156
30 3 3 9263064000150
34 2 3 9312770000144
54 1 3 8407830000140
55 1 3 5590100000139
city:
federation_unit_id name
id
3 8 SAO PAULO
4 8 CAMPINAS
7 8 BARUERI
8 8 BEBEDOURO
9 8 SANTOS
I want to merge them combining target's "city_id" with city's "id", in a way that the final dataframe looks like this:
我想合并它们，结合target'city_id' 和city'id'，最终数据帧如下所示：
target:
version city_id code federation_unit_id name
id
4 2 4 5736201000175 8 CAMPINAS
26 2 3 8290265000183 8 SAO PAULO
27 3 3 9529184000156 8 SAO PAULO
30 3 3 9263064000150 8 SAO PAULO
34 2 3 9312770000144 8 SAO PAULO
54 1 3 8407830000140 8 SAO PAULO
55 1 3 5590100000139 8 SAO PAULO
To achieve that, I'm trying to use the following code:
为了实现这一点，我正在尝试使用以下代码：
target=target.merge(city, left_on='city_id', right_on='id')
However it keeps getting me the following KeyError:
但是，它不断让我收到以下 KeyError：
Traceback (most recent call last):
File "/file.py", line 12, in <module>
target=target.merge(city, left_on='index', right_on='city_id')
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/pandas/core/frame.py", line 4437, in merge
copy=copy, indicator=indicator)
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/pandas/tools/merge.py", line 38, in merge
copy=copy, indicator=indicator)
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/pandas/tools/merge.py", line 210, in __init__
self.join_names) = self._get_merge_keys()
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/pandas/tools/merge.py", line 434, in _get_merge_keys
right_keys.append(right[rk]._values)
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/pandas/core/frame.py", line 1997, in __getitem__
return self._getitem_column(key)
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/pandas/core/frame.py", line 2004, in _getitem_column
return self._get_item_cache(key)
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/pandas/core/generic.py", line 1350, in _get_item_cache
values = self._data.get(item)
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/pandas/core/internals.py", line 3290, in get
loc = self.items.get_loc(item)
File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/pandas/indexes/base.py", line 1947, in get_loc
return self._engine.get_loc(self._maybe_cast_indexer(key))
File "pandas/index.pyx", line 137, in pandas.index.IndexEngine.get_loc (pandas/index.c:4154)
File "pandas/index.pyx", line 159, in pandas.index.IndexEngine.get_loc (pandas/index.c:4018)
File "pandas/hashtable.pyx", line 675, in pandas.hashtable.PyObjectHashTable.get_item (pandas/hashtable.c:12368)
File "pandas/hashtable.pyx", line 683, in pandas.hashtable.PyObjectHashTable.get_item (pandas/hashtable.c:12322)
KeyError: 'id'
I can't find out what am I doing wrong :/ Can someone help on that?
我不知道我做错了什么：/有人可以帮忙吗？
回答by piRSquared
You can use join
您可以使用 join
target.join(city, on='city_id')
joinis inherently index oriented. However, you can specify an alternative column to join on in the dataframe that constitutes the left side. If we call the joinmethod on targetthen we want to specify 'city_id'as that alternative column. The citydataframe already has the appropriate index.
join本质上是面向索引的。但是，您可以在构成左侧的数据框中指定要加入的替代列。如果我们调用该join方法，target那么我们希望指定'city_id'为该替代列。该city数据帧已经有合适的索引。
回答by Psidom
The idin the citydata frame seems to be an index, try set right_index=True:
将id在城市的数据帧似乎是一个指标，尽量设置right_index=True：
target.merge(city, left_on='city_id', right_index=True)
