python - 将列添加到 Pandas 数据框时如何避免列和 DatetimeIndex 之间的混淆

Question

我有一个 pandas DataFrame，其列标题是数字字符串，索引是 DatetimeIndex。例如:

In:
df=pd.DataFrame([[1,2,3],[4,5,6],[7,8,9]], index=pd.DatetimeIndex(['2019-01-01 00:00:00', '2019-01-01 00:05:00',
               '2019-01-01 00:10:00']), columns=['010000','010001','010002'])
df

Out:
                     010000  010001  010002
2019-01-01 00:00:00       1       2       3
2019-01-01 00:05:00       4       5       6
2019-01-01 00:10:00       7       8       9

我成功地将列添加到数据框，例如，

In:
df['010003'] = pd.Series([99,99,99], index= df.index)
df
Out: 
                     010000  010001  010002  010003
2019-01-01 00:00:00       1       2       3      99
2019-01-01 00:05:00       4       5       6      99
2019-01-01 00:10:00       7       8       9      99

但是，如果列标题可能被误认为是日期，Pandas 会将其视为索引元素，尝试添加行而不是列，并引发异常:

In:
df['010119'] = pd.Series([99,99,99], index= df.index)
Out:
Traceback (most recent call last):
  File "C:\Users\...\AppData\Local\Continuum\anaconda3\lib\site-packages\IPython\core\interactiveshell.py", line 3325, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-16-1f55509f2987>", line 1, in <module>
    df['010119'] = pd.Series([99,99,99], index= df.index)
  File "C:\Users\...\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\frame.py", line 3362, in __setitem__
    return self._setitem_slice(indexer, value)
  File "C:\Users\...\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\frame.py", line 3374, in _setitem_slice
    self.loc._setitem_with_indexer(key, value)
  File "C:\Users\...\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\indexing.py", line 656, in _setitem_with_indexer
    value=value)
  File "C:\Users\...\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\internals\managers.py", line 510, in setitem
    return self.apply('setitem', **kwargs)
  File "C:\Users\...\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\internals\managers.py", line 395, in apply
    applied = getattr(b, f)(**kwargs)
  File "C:\Users\...\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\internals\blocks.py", line 920, in setitem
    values[indexer] = value
ValueError: could not broadcast input array from shape (3) into shape (3,4)

为了避免这种困惑，我应该如何重写赋值以强制 Pandas 将数字字符串作为新列的标题？

Answer 1

我们有用于插入列的特定功能

df.insert(len(df.columns),column='010119',value=[99,99,99])
df
                     010000  010001  010002  010119
2019-01-01 00:00:00       1       2       3      99
2019-01-01 00:05:00       4       5       6      99
2019-01-01 00:10:00       7       8       9      99