正确的方法来反转pandas.DataFrame？

Question

这是我的代码：

import pandas as pd

data = pd.DataFrame({'Odd':[1,3,5,6,7,9], 'Even':[0,2,4,6,8,10]})

for i in reversed(data):
    print(data['Odd'], data['Even'])

当我运行此代码时，出现以下错误：

Traceback (most recent call last):
  File "C:\Python33\lib\site-packages\pandas\core\generic.py", line 665, in _get_item_cache
    return cache[item]
KeyError: 5

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\*****\Documents\******\********\****.py", line 5, in <module>
    for i in reversed(data):
  File "C:\Python33\lib\site-packages\pandas\core\frame.py", line 2003, in __getitem__
    return self._get_item_cache(key)
  File "C:\Python33\lib\site-packages\pandas\core\generic.py", line 667, in _get_item_cache
    values = self._data.get(item)
  File "C:\Python33\lib\site-packages\pandas\core\internals.py", line 1656, in get
    _, block = self._find_block(item)
  File "C:\Python33\lib\site-packages\pandas\core\internals.py", line 1936, in _find_block
    self._check_have(item)
  File "C:\Python33\lib\site-packages\pandas\core\internals.py", line 1943, in _check_have
    raise KeyError('no item named %s' % com.pprint_thing(item))
KeyError: 'no item named 5'

为什么会出现此错误？
我该如何解决？
正确的逆转方法是pandas.DataFrame什么？

Answer 1

data.reindex(index=data.index[::-1])

或者简单地：

data.iloc[::-1]

将反转您的数据帧，如果您想使for循环从下到上，则可以执行以下操作：

for idx in reversed(data.index):
    print(idx, data.loc[idx, 'Even'], data.loc[idx, 'Odd'])

要么

for idx in reversed(data.index):
    print(idx, data.Even[idx], data.Odd[idx])

因为你得到一个错误reversed首先调用data.__len__()返回6，然后试图调用data[j - 1]用于j在range(6, 0, -1)和第一个电话会data[5];
但在pandas数据框中data[5]表示第5列，而没有第5列，因此它将引发异常。（请参阅文档）