AssertionError:unstack()数据帧时，blk ref_locs中存在间隙 [英] AssertionError: Gaps in blk ref_locs when unstack() dataframe

问题描述

我正在尝试将Pandas数据框中的数据进行stack()，但是我一直收到此错误，并且我不确定为什么.到目前为止，这是我的代码，并提供了我的数据样本.我试图解决此问题的方法是删除voteId不是数字的所有行，这不适用于我的实际数据集.当我部署代码时，这在Anaconda笔记本(我正在开发的笔记本)和生产环境中都会发生.

I am trying to unstack() data in a Pandas dataframe, but I keep getting this error, and I'm not sure why. Here is my code so far with a sample of my data. My attempt to fix it was to remove all rows where voteId was not a number, which did not work with my actual dataset. This is happening both in an Anaconda notebook (where I am developing) and in my production env when I deploy the code.

我无法弄清楚如何在示例代码中重现错误……可能是由于实例化数据帧时不存在类型转换问题，就像我在示例中所做的那样?

I could not figure out how to reproduce the error in my sample code... possibly due to a typecasting issue that doesnt exist when you instantiate the dataframe like I did in the sample?

#dataset simulate likely input
# d = {'vote': [100, 50,1,23,55,67,89,44], 
#      'vote2': [10, 2,18,26,77,99,9,40], 
#      'ballot1': ['a','b','a','a','b','a','c','c'],
#      'voteId':[1,2,3,4,5,'aaa',7,'NaN']}
# df1=pd.DataFrame(d)
#########################################################

df1=df1.drop_duplicates(['voteId','ballot1'],keep='last')

s=df1[:10].set_index(['voteId','ballot1'],verify_integrity=True).unstack()
s.columns=s.columns.map('(ballot1={0[1]}){0[0]}'.format) 
dflw=pd.DataFrame(s)

完整的错误消息/堆栈跟踪:

Full error message/stack trace:

---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
<ipython-input-10-0a520180a8d9> in <module>()
     22 df1=df1.drop_duplicates(['voteId','ballot1'],keep='last')
     23 
---> 24 s=df1[:10].set_index(['voteId','ballot1'],verify_integrity=True).unstack()
     25 s.columns=s.columns.map('(ballot1={0[1]}){0[0]}'.format)
     26 dflw=pd.DataFrame(s)

~/anaconda3/lib/python3.6/site-packages/pandas/core/frame.py in unstack(self, level, fill_value)
   4567         """
   4568         from pandas.core.reshape.reshape import unstack
-> 4569         return unstack(self, level, fill_value)
   4570 
   4571     _shared_docs['melt'] = ("""

~/anaconda3/lib/python3.6/site-packages/pandas/core/reshape/reshape.py in unstack(obj, level, fill_value)
    467     if isinstance(obj, DataFrame):
    468         if isinstance(obj.index, MultiIndex):
--> 469             return _unstack_frame(obj, level, fill_value=fill_value)
    470         else:
    471             return obj.T.stack(dropna=False)

~/anaconda3/lib/python3.6/site-packages/pandas/core/reshape/reshape.py in _unstack_frame(obj, level, fill_value)
    480         unstacker = partial(_Unstacker, index=obj.index,
    481                             level=level, fill_value=fill_value)
--> 482         blocks = obj._data.unstack(unstacker)
    483         klass = type(obj)
    484         return klass(blocks)

~/anaconda3/lib/python3.6/site-packages/pandas/core/internals.py in unstack(self, unstacker_func)
   4349         new_columns = new_columns[columns_mask]
   4350 
-> 4351         bm = BlockManager(new_blocks, [new_columns, new_index])
   4352         return bm
   4353 

~/anaconda3/lib/python3.6/site-packages/pandas/core/internals.py in __init__(self, blocks, axes, do_integrity_check, fastpath)
   3035         self._consolidate_check()
   3036 
-> 3037         self._rebuild_blknos_and_blklocs()
   3038 
   3039     def make_empty(self, axes=None):

~/anaconda3/lib/python3.6/site-packages/pandas/core/internals.py in _rebuild_blknos_and_blklocs(self)
   3127 
   3128         if (new_blknos == -1).any():
-> 3129             raise AssertionError("Gaps in blk ref_locs")
   3130 
   3131         self._blknos = new_blknos

AssertionError: Gaps in blk ref_locs

推荐答案

要获取触发异常的真实数据，请添加其他调试信息

To get the real data triggered the exception, add extra debug information

修改~/anaconda3/lib/python3.6/site-packages/pandas/core/internals.py

将行添加到class BlockManager()

def __init__(self)
    print('BlockManager blocks')
    pprint(self.blocks)
    print('BlockManager axes')
    pprint(self.axes)

您将获得数据:

_unstack_frame level -1 fill_value None 

                 vote  vote2
ballot1 voteId              
NaN     xx      100.0   10.0
False   aaa      50.1    2.0
-1      \n        1.0   18.0
True    NaN      23.0   26.0
b       False    55.0   77.0
a       \        67.0   99.0
c                89.0    9.0
        8        44.0    NaN

修改~/anaconda3/lib/python3.6/site-packages/pandas/core/reshape/reshape.py

def __unstack_frame(self, ...)
    from pprint import pprint
    print('_unstack_frame level {} fill_value {} {}'.format(level, fill_value, type(obj)))
    pprint(obj)

您将看到数据:

BlockManager blocks
(FloatBlock: slice(0, 16, 1), 16 x 8, dtype: float64,)
BlockManager axes
[MultiIndex(levels=[[u'vote', u'vote2'], [False, 8, u'\n', u' ', u'\', u'aaa', u'xx']],
           labels=[[0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1], [-1, 0, 1, 2, 3, 4, 5, 6, -1, 0, 1, 2, 3, 4, 5, 6]],
           names=[None, u'voteId']),
 Index([nan, -1, False, True, u'', u'a', u'b', u'c'], dtype='object', name=u'ballot1')]

我确实触发了另一个例子的异常:

I did trigger an exception with another example:

  File "/usr/lib64/python2.7/site-packages/pandas/core/internals.py", line 2902, in _rebuild_blknos_and_blklocs
    raise AssertionError("Gaps in blk ref_locs")
AssertionError: Gaps in blk ref_locs

带有调试信息

BlockManager blocks
(FloatBlock: [-1, -1, -1], 3 x 2, dtype: float64,)
BlockManager axes
[Index([aaa, bbb, ccc], dtype='object'), Int64Index([0, 1], dtype='int64')]

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