熊猫数据框中的numpy datetime64

Question

我有一个 pandas DataFrame 由 3 列组成，第一列是 dtype 的每小时时间序列 np.datetime64

import numpy as np
import pandas as pd    
timeseries = np.arange(np.datetime64('20/11/2009'), np.datetime64('19/11/2010), np.timedelta64(1, 'h'))
insolation =pd.DataFrame(columns=['datetime','GHI','DNI'])
insolation['datetime'] = timeseries

如果我 print(insolation) 我得到这个输出：

                   datetime  GHI  DNI
0    2009-11-20 00:00:00  NaN  NaN
1    2009-11-20 01:00:00  NaN  NaN
2    2009-11-20 02:00:00  NaN  NaN
...                  ...  ...  ...
8734 2010-11-18 22:00:00  NaN  NaN
8735 2010-11-18 23:00:00  NaN  NaN

到目前为止，一切都很好。但是如果我使用这个 datetime64 对象：

datetime=np.datetime64('2009-11-20 00:00:00')

（似乎确实存在于 DataFrame 中）来引用 DataFrame：

insolation[datetime][GHI] =1.0

我收到一个错误：

KeyError: numpy.datetime64('2009-11-20T00:00:00')

完整的错误信息如下：

Traceback (most recent call last):
  File "C:\Users\z5044992\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\indexes\base.py", line 1945, in get_loc
    return self._engine.get_loc(key)
  File "pandas\index.pyx", line 137, in pandas.index.IndexEngine.get_loc (pandas\index.c:4154)
  File "pandas\index.pyx", line 159, in pandas.index.IndexEngine.get_loc (pandas\index.c:4018)
  File "pandas\hashtable.pyx", line 675, in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12368)
  File "pandas\hashtable.pyx", line 683, in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12322)
KeyError: numpy.datetime64('2009-11-20T00:00:00')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:/PYTHONprojects/PY_EN_Models/Scripts/create_weatherfile.py", line 109, in <module>
    main()
  File "C:/PYTHONprojects/PY_EN_Models/Scripts/create_weatherfile.py", line 87, in main
    insolation[datetime][GHI] = irradience_array[gridrow,gridcol]
  File "C:\Users\z5044992\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\frame.py", line 1997, in __getitem__
    return self._getitem_column(key)
  File "C:\Users\z5044992\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\frame.py", line 2004, in _getitem_column
    return self._get_item_cache(key)
  File "C:\Users\z5044992\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\generic.py", line 1350, in _get_item_cache
    values = self._data.get(item)
  File "C:\Users\z5044992\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\internals.py", line 3290, in get
    loc = self.items.get_loc(item)
  File "C:\Users\z5044992\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\indexes\base.py", line 1947, in get_loc
    return self._engine.get_loc(self._maybe_cast_indexer(key))
  File "pandas\index.pyx", line 137, in pandas.index.IndexEngine.get_loc (pandas\index.c:4154)
  File "pandas\index.pyx", line 159, in pandas.index.IndexEngine.get_loc (pandas\index.c:4018)
  File "pandas\hashtable.pyx", line 675, in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12368)
  File "pandas\hashtable.pyx", line 683, in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12322)
KeyError: numpy.datetime64('2009-11-20T00:00:00')

Process finished with exit code 1

Answer 1

使用loc

insolation.loc[insolation.datetime.eq(datetime), 'GHI'] = 1.0

---

出了什么问题？

insolation[datetime]

尝试获取由变量 datetime 定义的列。
提示：不要使用与列名相同的变量名。