重新索引错误毫无意义

问题描述

我的 DataFrames 的大小介于100k和2m之间。我正在处理这个问题的那个很大，但请注意我必须对其他帧做同样的事情：

I have DataFrames between 100k and 2m in size. the one I am dealing with for this question is this large, but note that I will have to do the same for the other frames:

>>> len(data)
357451

现在这个文件是通过编译许多文件创建的，所以它的索引真的很奇怪。所以我想做的就是用范围（len（数据））重新索引它，但是我收到了这个错误：

now this file was created by compiling many files, so the index for it is really odd. So all I wanted to do was reindex it with range(len(data)), but I get this error:

>>> data.reindex(index=range(len(data)))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pandas/core/frame.py", line 2542, in reindex
    fill_value, limit)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pandas/core/frame.py", line 2618, in _reindex_index
    limit=limit)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pandas/core/index.py", line 893, in reindex
    limit=limit)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pandas/core/index.py", line 812, in get_indexer
    raise Exception('Reindexing only valid with uniquely valued Index '
Exception: Reindexing only valid with uniquely valued Index objects

这实际上没有任何意义。由于我使用包含数字0到357450的数组重新索引，所有Index对象都是唯一的！为什么它是retu发生此错误？

This actually makes no sense. Since I am reindexing with an array containing numbers 0 through 357450, all Index objects are unique! Why is it returning this error?

额外信息：我使用的是python2.7和pandas 11.0

Extra info: I am using python2.7 and pandas 11.0

推荐答案

当它抱怨重新索引仅对具有唯一值的索引有效时，它并不反对你的 new 索引不是唯一的，它反对你的旧索引不是。

When it complains that Reindexing only valid with uniquely valued Index, it's not objecting that your new index isn't unique, it's objecting that your old one isn't.

例如：

>>> df = pd.DataFrame(range(5), index = [1,2,3,1,2])
>>> df
   0
1  0
2  1
3  2
1  3
2  4
>>> df.reindex(index=range(len(df)))
Traceback (most recent call last):
[...]
  File "/usr/local/lib/python2.7/dist-packages/pandas-0.12.0.dev_0bd5e77-py2.7-linux-i686.egg/pandas/core/index.py", line 849, in get_indexer
    raise Exception('Reindexing only valid with uniquely valued Index '
Exception: Reindexing only valid with uniquely valued Index objects

但是

>>> df.index = range(len(df))
>>> df
   0
0  0
1  1
2  2
3  3
4  4

虽然我想我写了

df.reset_index(drop=True)

而不是。

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