我正在尝试在python中实现决策树id3代码不知道这个错误是什么意思

如何解决我正在尝试在python中实现决策树id3代码不知道这个错误是什么意思

这是我的代码。

def train(x_train,tree=None):
    features = x_train.keys()[:-1]
    info_gains=[]

    for ix in features:
      i_gain=info_gain(x_train,ix)
      info_gains.append(i_gain)

    fkey=features[np.argmax(info_gain)]

    print(fkey +" has been selected as root")

    if tree is None:                    
        tree={}
        tree[fkey] = {}

    elt=divide_Dataset(x_train,fkey)

    for i in elt:
      clValue,counts = np.unique(i['salary_more_then_100k'],return_counts=True)

      if len(counts)==1:
        tree[fkey][i[fkey].values[0]] = clValue[0]                                                    
      else:
        tree[fkey][i[fkey].values[0]] = train(i)

    return tree

这是错误：

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
/usr/local/lib/python3.6/dist-packages/pandas/core/indexes/base.py in get_loc(self,key,method,tolerance)
   2645             try:
-> 2646                 return self._engine.get_loc(key)
   2647             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.Int64HashTable.get_item()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()

KeyError: 0

During handling of the above exception,another exception occurred:

KeyError                                  Traceback (most recent call last)
9 frames
/usr/local/lib/python3.6/dist-packages/pandas/core/indexes/base.py in get_loc(self,tolerance)
   2646                 return self._engine.get_loc(key)
   2647             except KeyError:
-> 2648                 return self._engine.get_loc(self._maybe_cast_indexer(key))
   2649         indexer = self.get_indexer([key],method=method,tolerance=tolerance)
   2650         if indexer.ndim > 1 or indexer.size > 1:

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.Int64HashTable.get_item()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()

KeyError: 0

我正在尝试在python中实现决策树id3代码。不知道此错误意味着什么。我认为train（i）的递归步骤中存在一些问题。