将列添加到数据帧键错误："2019-12-07 21：19：17"

Question

我有一个数据帧df，如下所示：

Name
0   John
1  Sarah 
2  Harry 
3    Bob
4     Jo
5  Steve
6    Leo 
7  Nigel

我正在尝试添加一个名为Last_Paid的列，其中新列中的所有行都包含上次修改支付文件的日期。

所需的输出如下所示：

Name            Last_Paid
0   John  2019-12-07 21:19:17
1  Sarah  2019-12-07 21:19:17
2  Harry  2019-12-07 21:19:17
3    Bob  2019-12-07 21:19:17
4     Jo  2019-12-07 21:19:17
5  Steve  2019-12-07 21:19:17
6    Leo  2019-12-07 21:19:17
7  Nigel  2019-12-07 21:19:17

我用来添加带有日期的列的代码如下：

modTimesinceEpoc = os.path.getmtime(PayFilepath)
LastmodificationTimePayfile = time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(modTimesinceEpoc))
df['Last_Paid'] = df[LastmodificationTimePayfile]

但是我得到了一个key error：

KeyError: '2019-12-07 21:19:17'

'2019-12-07 21:19:17'是LastmodificationTimePayfile变量的值

如何添加带有值的新列？

以下是完整的错误消息：

File "<ipython-input-13-48aa2b889a2a>", line 1, in <module>
runfile('C:/Database/Standardised Joined Q1 and Pay/2016_Q1/join.py', wdir='C:/Database/Standardised Joined Q1 and Pay/2016_Q1')
File "C:Anaconda_Python 3.72019.03libsite-packagesspyder_kernelscustomizespydercustomize.py", line 786, in runfile
execfile(filename, namespace)
File "C:Anaconda_Python 3.72019.03libsite-packagesspyder_kernelscustomizespydercustomize.py", line 110, in execfile
exec(compile(f.read(), filename, 'exec'), namespace)
File "C:/Database/Standardised Joined Q1 and Pay/2016_Q1/join.py", line 198, in <module>
main()
File "C:/Database/Standardised Joined Q1 and Pay/2016_Q1/join.py", line 85, in main
result['PAY_LAST_MODIFIED'] = result[LastmodificationTimePayfile]
File "C:Anaconda_Python 3.72019.03libsite-packagespandascoreframe.py", line 2927, in __getitem__
indexer = self.columns.get_loc(key)
File "C:Anaconda_Python 3.72019.03libsite-packagespandascoreindexesbase.py", line 2659, in get_loc
return self._engine.get_loc(self._maybe_cast_indexer(key))
File "pandas/_libs/index.pyx", line 108, in pandas._libs.index.IndexEngine.get_loc
File "pandas/_libs/index.pyx", line 127, in pandas._libs.index.IndexEngine.get_loc
File "pandas/_libs/index.pyx", line 153, in pandas._libs.index.IndexEngine._get_loc_duplicates
File "pandas/_libs/index.pyx", line 170, in pandas._libs.index.IndexEngine._maybe_get_bool_indexer
KeyError: '2019-12-07 21:19:17'

Answer 1

LastmodificationTimePayfile的值不是数据帧的列 - 因此是keyerror。

如果要将新列的值设置为LastmodificationTimePayfile的值，则应编写

df['Last_Paid'] = LastmodificationTimePayfile