Pandas - 手动创建数据框并插入值

Question

这是我的代码:

import pandas as pd
df = pd.DataFrame(columns = ["A", "B"])
df.iloc[0]['A'] = 5

这是输出:

Traceback (most recent call last):
  File "K:/Dop/Pentas/Simpletest/Temp.py", line 38, in <module>
    df.iloc[0]['A'] = 5
  File "C:\Python34\lib\site-packages\pandas\core\indexing.py", line 1189, in __getitem__
    return self._getitem_axis(key, axis=0)
  File "C:\Python34\lib\site-packages\pandas\core\indexing.py", line 1480, in _getitem_axis
    return self._get_loc(key, axis=axis)
  File "C:\Python34\lib\site-packages\pandas\core\indexing.py", line 89, in _get_loc
    return self.obj._ixs(key, axis=axis)
  File "C:\Python34\lib\site-packages\pandas\core\frame.py", line 1719, in _ixs
    label = self.index[i]
  File "C:\Python34\lib\site-packages\pandas\core\index.py", line 1076, in __getitem__
    return getitem(key)
IndexError: index 0 is out of bounds for axis 0 with size 0

有关如何修复它的任何建议？我事先不知道我的数据框的整体大小，但我可以猜测。

Answer 1

您可以使用数据初始化数据帧
df = pd.DataFrame(columns=["A", "B"], data=[[5,np.nan]]) ,

或使用 set_value方法(顺便说一下，它比 iloc 快得多):df.set_value(0,'A',5)
更新 2018-04-12 ⬇

由于 Pandas 版本 0.21.0 df.set_value已弃用。您应该使用 .at[]或 .iat[]取而代之的是:

df.at[0, 'A'] = 5