只需将pandas.DataFrame子类化并像这样包装loc：
import pandas.DataFrame
class XXX(pandas.DataFrame):
def __init__(self):
super(Override, self).__init__(columns=['operation'])
def add_row(self, index, value):
self.loc[index] = value
这是添加行时得到的：
============================= ERRORS =============================
Traceback (most recent call last):
File "/home/samuel/git/xxx/tests/test_xxx.py", line 21, in setUp
self.override.add_override(ticker, override)
File "/home/samuel/git/xxx/xxx.py", line 198, in add_override
self.loc[ticker] = override
File "/home/samuel/.local/lib/python2.7/site-packages/pandas/core/indexing.py", line 190, in __setitem__
self._setitem_with_indexer(indexer, value)
File "/home/samuel/.local/lib/python2.7/site-packages/pandas/core/indexing.py", line 451, in _setitem_with_indexer
self.obj._data = self.obj.append(value)._data
File "/home/samuel/.local/lib/python2.7/site-packages/pandas/core/frame.py", line 6692, in append
sort=sort)
File "/home/samuel/.local/lib/python2.7/site-packages/pandas/core/reshape/concat.py", line 229, in concat
return op.get_result()
File "/home/samuel/.local/lib/python2.7/site-packages/pandas/core/reshape/concat.py", line 431, in get_result
return (cons._from_axes(new_data, self.new_axes)
File "/home/samuel/.local/lib/python2.7/site-packages/pandas/core/generic.py", line 341, in _from_axes
return cls(data, **kwargs)
TypeError: __init__() takes exactly 1 argument (2 given)