将 cftime.DatetimeJulian 转换为日期时间

Question

我正在尝试将 xarray 数据数组转换为机器学习项目的 pandas 数据帧，但时间数据似乎是 cftime.DatetimeJulian 格式，这不能使用 pandas to_datetime() 方法转换。建议？谢谢。

nor_xr.time

<xarray.DataArray 'time' (time: 1372)>
array([cftime.DatetimeJulian(2015, 3, 31, 0, 0, 0, 0, 0, 90),
       cftime.DatetimeJulian(2018, 12, 31, 0, 0, 0, 0, 6, 365)], dtype=object)
Coordinates:
  * time     (time) object 2015-03-31 00:00:00 ... 2018-12-31 00:00:00
Attributes:
    standard_name:  time
    axis:           T

nor_df = nor_xr.to_dataframe().reset_index()
nor_df.head()

    time
0   2015-03-31 00:00:00
1   2015-04-01 00:00:00

pd.to_datetime(nor_df.time)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-104-1f0fc00ad825> in <module>
      2 
      3 #|nor_df.time.unique()
----> 4 pd.to_datetime(nor_df.time)

~\AppData\Local\Continuum\anaconda3A\lib\site-packages\pandas\core\tools\datetimes.py in to_datetime(arg, errors, dayfirst, yearfirst, utc, box, format, exact, unit, infer_datetime_format, origin, cache)
    449         else:
    450             from pandas import Series
--> 451             values = _convert_listlike(arg._values, True, format)
    452             result = Series(values, index=arg.index, name=arg.name)
    453     elif isinstance(arg, (ABCDataFrame, MutableMapping)):

~\AppData\Local\Continuum\anaconda3A\lib\site-packages\pandas\core\tools\datetimes.py in _convert_listlike(arg, box, format, name, tz)
    366                     dayfirst=dayfirst,
    367                     yearfirst=yearfirst,
--> 368                     require_iso8601=require_iso8601
    369                 )
    370 

pandas\_libs\tslib.pyx in pandas._libs.tslib.array_to_datetime()

pandas\_libs\tslib.pyx in pandas._libs.tslib.array_to_datetime()

pandas\_libs\tslib.pyx in pandas._libs.tslib.array_to_datetime()

TypeError: <class 'cftime._cftime.DatetimeJulian'> is not convertible to datetime

Answer 1

确实这是一个常见的请求。推荐的做法是拉出索引（一个CFTimeIndex) and use its built-in to_datetimeindex方法：

datetimeindex = nor_xr.indexes['time'].to_datetimeindex()

然后您可以将 CFTimeIndex 替换为对应的 DatetimeIndex：

nor_xr['time'] = datetimeindex

Answer 2

我找到了一种从 cftime.DatetimeNoLeap 转换为 datetime 对象的简单方法。例如说 datetimes 是 cftime.DatetimeNoLeap 个对象的列表日期时间[0] = cftime.DatetimeNoLeap(1970, 1, 1, 12, 0, 0, 0, has_year_zero=True)

datetime.strptime(str(datetimes[0]),'%Y-%m-%d %H:%M:%S')

这会给你 datetime.datetime(1970, 1, 1, 12, 0).

将 cftime.DatetimeJulian 转换为日期时间

Converting cftime.DatetimeJulian to datetime

python

pandas

python-xarray