小编典典

反转熊猫数据框的正确方法?

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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,我收到以下错误:

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'

为什么我会收到此错误?
我该如何解决?
什么是正确的反转方法pandas.DataFrame


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2022-07-06

共1个答案

小编典典

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

或者简单地说:

data.iloc[::-1]

将反转您的数据框,如果您想要一个for从下到上的循环,您可以这样做:

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

或者

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

您收到一个错误,因为reversed第一次调用data.__len__()返回 6。然后它尝试调用in data[j - 1],第一次调用将是;
但在熊猫数据框中表示第 5 列,并且没有第 5
列,因此它会引发异常。(见文档j``range(6, 0, -1)``data[5]``data[5]

2022-07-06