python - 通过多列 Pandas 解析

数据如下：

raw_data = {'first_name': ['Jason', 'Jason', 'Tina', 'Jake', 'Amy'],
            'last_name': ['Miller', 'Miller', 'Ali', 'Milner', 'Cooze'],
            'age': [42, 42, 36, 24, 73],
            'preTestScore': [4, 4, 31, 2, 3],
            'postTestScore': [25, 25, 57, 62, 70]}
df = pd.DataFrame(raw_data, columns = ['first_name', 'last_name', 'age', 'preTestScore', 'postTestScore'])

现在，我想搜索数据框并查找两个列值，以获取对应的两个列值。

这是我尝试过的

a,b=df['first_name','last_name'].where(df['age','preTestScore']==42,4)

但是它得到了错误

KeyError                                  Traceback (most recent call last)
E:\anaconda\lib\site-packages\pandas\core\indexes\base.py in get_loc(self, key, method, tolerance)
   3063             try:
-> 3064                 return self._engine.get_loc(key)
   3065             except KeyError:

pandas\_libs\index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas\_libs\index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas\_libs\hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

pandas\_libs\hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

KeyError: ('first_name', 'last_name')

During handling of the above exception, another exception occurred:

KeyError                                  Traceback (most recent call last)
<ipython-input-6-07dc94043416> in <module>()
----> 1 a,b=df['first_name','last_name'].where(df['age','preTestScore']==42,4)

E:\anaconda\lib\site-packages\pandas\core\frame.py in __getitem__(self, key)
   2686             return self._getitem_multilevel(key)
   2687         else:
-> 2688             return self._getitem_column(key)
   2689
   2690     def _getitem_column(self, key):

E:\anaconda\lib\site-packages\pandas\core\frame.py in _getitem_column(self, key)
   2693         # get column
   2694         if self.columns.is_unique:
-> 2695             return self._get_item_cache(key)
   2696
   2697         # duplicate columns & possible reduce dimensionality

E:\anaconda\lib\site-packages\pandas\core\generic.py in _get_item_cache(self, item)
   2484         res = cache.get(item)
   2485         if res is None:
-> 2486             values = self._data.get(item)
   2487             res = self._box_item_values(item, values)
   2488             cache[item] = res

E:\anaconda\lib\site-packages\pandas\core\internals.py in get(self, item, fastpath)
   4113
   4114             if not isna(item):
-> 4115                 loc = self.items.get_loc(item)
   4116             else:
   4117                 indexer = np.arange(len(self.items))[isna(self.items)]

E:\anaconda\lib\site-packages\pandas\core\indexes\base.py in get_loc(self, key, method, tolerance)
   3064                 return self._engine.get_loc(key)
   3065             except KeyError:
-> 3066                 return self._engine.get_loc(self._maybe_cast_indexer(key))
   3067
   3068         indexer = self.get_indexer([key], method=method, tolerance=tolerance)

pandas\_libs\index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas\_libs\index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas\_libs\hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

pandas\_libs\hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

KeyError: ('first_name', 'last_name')

最佳答案

您可以使用set_index将索引转换为MultiIndex ('age', 'preTestScore')。然后将pd.DataFrame.loc与行和列标签一起使用：

df2 = df.set_index(['age', 'preTestScore'])

cols = ['first_name', 'last_name']
res = df2.loc[(42, 4), cols].values.tolist()

print(res)

[['Jason', 'Miller']]

关于python - 通过多列 Pandas 解析，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/51246259/