计算熊猫数据框中的行均值时，iterrows（）中出现意外的KeyError

Question

我有一个更大的数据框，但是出于我的问题，我正在用这个小df重新创建它。然后我得到这个错误的结果。 我不明白为什么，因为这个df非常简单，应该可以正常工作吗？

data = [{'0':2,'1':4,'2':6}, {'0':10,'1':20,'2':30}]
df1 = pd.DataFrame(data,index=[1994,1995])
df1

for index,row in df1.iterrows():
    means=df1[index].mean()     

    print(means)

我想重现这段代码，以查看它与df1.mean（axis = 1）的比较，因为我在原始大数据框中得到了不同的均值结果，并且 我想深入了解这一点。上面的代码在我的大df中运行良好！

~\Anaconda3\lib\site-packages\pandas\core\indexes\base.py in get_loc(self, key, method, tolerance)
   3062             try:
-> 3063                 return self._engine.get_loc(key)
   3064             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: 1994

During handling of the above exception, another exception occurred:

KeyError                                  Traceback (most recent call last)
<ipython-input-31-4619f3f796db> in <module>()
      1 for index,row in df1.iterrows():
----> 2     means=df1[index].mean()
      3 
      4     print(means)

~\Anaconda3\lib\site-packages\pandas\core\frame.py in __getitem__(self, key)
   2683             return self._getitem_multilevel(key)
   2684         else:
-> 2685             return self._getitem_column(key)
   2686 
   2687     def _getitem_column(self, key):

~\Anaconda3\lib\site-packages\pandas\core\frame.py in _getitem_column(self, key)
   2690         # get column
   2691         if self.columns.is_unique:
-> 2692             return self._get_item_cache(key)
   2693 
   2694         # duplicate columns & possible reduce dimensionality

~\Anaconda3\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

~\Anaconda3\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)]

~\Anaconda3\lib\site-packages\pandas\core\indexes\base.py in get_loc(self, key, method, tolerance)
   3063                 return self._engine.get_loc(key)
   3064             except KeyError:
-> 3065                 return self._engine.get_loc(self._maybe_cast_indexer(key))
   3066 
   3067         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: 1994