追加HDFStore失败，无法匹配现有的表结构

Question

尝试通过pd.HDFStore('mystore.h5', mode='a').append(my_frame, chunk)将数据帧以小块形式发送到hdf5时遇到问题。块在列和类型方面都是相同的（它们来自同一个数据帧），但它适用于很多块，然后在中途爆炸。在

ValueError: cannot match existing table structure for [Net_Bal_Amt,Loan_Current_Rate] on appending data

我打印出导致失败的dataframe块，它们的一个共同点是特定列的所有'None'值（它们最初从源代码中为null）。不知道该怎么纠正。它们应该保持None或NaN或null，只要它们是空的。谢谢。在

Traceback (most recent call last):
  File "[...]\Anaconda3\lib\site-packages\pandas\io\pytables.py", line 3381, in create_axes
    b, b_items = by_items.pop(items)
KeyError: ('Net_Bal_Amt', 'Loan_Current_Rate')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "[...]\crd_test.py", line 8, in <module>
    credit.CRD.hdf_install(overwrite=True, tablenames=['loans_uscrd', 'loans_uscrd_a'])
  File "[...]\credit_base.py", line 62, in hdf_install
    cls._hdf_creation(map_)
  File "[...]\credit_base.py", line 80, in _hdf_creation
    cls._hdf_processing(v, chunk)
  File "[...]\credit_base.py", line 88, in _hdf_processing
    cls.crd.append(frame, chunk)   
  File "[...]\Anaconda3\lib\site-packages\pandas\io\pytables.py", line 903, in append
    **kwargs)
  File "[...]\lib\site-packages\pandas\io\pytables.py", line 1259, in _write_to_group
    s.write(obj=value, append=append, complib=complib, **kwargs)
  File "[...]\lib\site-packages\pandas\io\pytables.py", line 3751, in write
    **kwargs)
  File "[...]\Anaconda3\lib\site-packages\pandas\io\pytables.py", line 3388, in create_axes
    item in items))
ValueError: cannot match existing table structure for [Net_Bal_Amt,Loan_Current_Rate] on appending data

数据类型：

^{pr2}$

版本： pytables:3.1.1 熊猫：0.15.2 python:3.4在

崩溃时追加的数据块类型：

Customer_Id                  object
As_of_Date           datetime64[ns]
Net_Bal_Amt                 float64
Loan_Current_Rate            object
dtype: object