无法使用 loc 更新列中的 nan 值？

Question

我已经存储了该列在索引中缺少值的所有记录的索引值，并且我正在尝试根据两个数据帧中常见的“StockCode”列从另一个数据帧中估算 nan 值。

这就是 df_mod 的样子。 df 也相同，但描述为 nan。索引是数组，如 [1,2,3,4] snapshot of df_mod

for i in index:
    if df.loc[i,'StockCode'] in df_mod['StockCode'].values:
        df.loc[i,'Description']=df_mod.loc[(df_mod.StockCode==df.loc[i,'StockCode']),'Description']

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-201-ada042d0d5a1> in <module>
      1 for i in index:
      2     if df.loc[i,'StockCode'] in df_mod['StockCode'].values:
----> 3         df.loc[i,'Description']=df_mod.loc[(df_mod.StockCode==df.loc[i,'StockCode']),'Description']

D:\Anaconda\lib\site-packages\pandas\core\indexing.py in __setitem__(self, key, value)
    188             key = com.apply_if_callable(key, self.obj)
    189         indexer = self._get_setitem_indexer(key)
--> 190         self._setitem_with_indexer(indexer, value)
    191 
    192     def _validate_key(self, key, axis):

D:\Anaconda\lib\site-packages\pandas\core\indexing.py in _setitem_with_indexer(self, indexer, value)
    467 
    468             if isinstance(value, ABCSeries):
--> 469                 value = self._align_series(indexer, value)
    470 
    471             info_idx = indexer[info_axis]

D:\Anaconda\lib\site-packages\pandas\core\indexing.py in _align_series(self, indexer, ser, multiindex_indexer)
    781             return ser.reindex(ax)._values
    782 
--> 783         raise ValueError('Incompatible indexer with Series')
    784 
    785     def _align_frame(self, indexer, df):

ValueError: Incompatible indexer with Series

Answer 1

没有（样本）您的数据，很难说。但这可能是replace 的情况：

df['Description'] = df['StockCode'].replace(df_mod.set_index('StockCode')['Description'])