da.loc[date[0]] brings up two instead of one

Problem description

My dataset has lots of days, with data for two times for each day: midnight and midday (12am and 12pm). With date[0], I am trying to retrieve only the midnight data from the first day; with date[1], the midday data from the same day; date[3] the midnight data from the next day, etc. Now I’m writing this, I’m not sure I’ve posted this in the right place so please let me know if I haven’t.

Code Sample 1: this gives data for midnight and midday (time: 2)

from datetime import datetime, timedelta
start = datetime(1979, 1, 1)
date = [start.strftime('%Y%m%d')]
a = first_dataset.loc[date[0]]
print(a)

<xarray.DataArray (time: 2, latitude: 241, longitude: 480)>
array([[[  #there are numbers here, cut out for ease of reading
            ]]])
Coordinates:
  * longitude  (longitude) float32 0.0 0.75 1.5 2.25 3.0 3.75 4.5 5.25 6.0 ...
  * latitude   (latitude) float32 90.0 89.25 88.5 87.75 87.0 86.25 85.5 ...
  * time       (time) datetime64[ns] 1979-01-01 1979-01-01 T12:00:00 #as you can see here, for
#midnight the time is just 1979-01-01 instead of 1979-01-01 00:00:00, which I think might be causing
#some confusion in my code

Code Sample 2: try adding hour to the date

from datetime import datetime, timedelta
start = datetime(1979, 1, 1)
date = [start.strftime('%Y%m%d%H')] #this what I changed
a = first_dataset.loc[date[0]]
print(a)

Traceback (most recent call last):
  File "pandas/index.pyx", line 589, in pandas.index.DatetimeEngine.get_loc (pandas/index.c:11661)
  File "pandas/src/hashtable_class_helper.pxi", line 404, in pandas.hashtable.Int64HashTable.get_item (pandas/hashtable.c:8543)
TypeError: an integer is required
 
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/nerc/n02/n02/amethyst/.conda/envs/my_root/lib/python3.4/site-packages/pandas/indexes/base.py", line 2134, in get_loc
    return self._engine.get_loc(key)
  File "pandas/index.pyx", line 553, in pandas.index.DatetimeEngine.get_loc (pandas/index.c:11829)
  File "pandas/index.pyx", line 591, in pandas.index.DatetimeEngine.get_loc (pandas/index.c:11735)
  File "pandas/index.pyx", line 597, in pandas.index.DatetimeEngine._date_check_type (pandas/index.c:11899)
KeyError: '1979010100'

Expected Output

a = first_dataset.loc[date[0]]
print(a)

<xarray.DataArray (time: 1, latitude: 241, longitude: 480)>
array([[[  #there are numbers here, cut out for ease of reading
            ]]])
Coordinates:
  * longitude  (longitude) float32 0.0 0.75 1.5 2.25 3.0 3.75 4.5 5.25 6.0 ...
  * latitude   (latitude) float32 90.0 89.25 88.5 87.75 87.0 86.25 85.5 ...
  * time       (time) datetime64[ns] 1979-01-01

[am-thyst]

@spencerkclark yeah I was using a different platform, updated my xarray version and this works now, thanks!

[spencerkclark]

This seems like an xarray version issue; the other argument was not added to where until version 0.10.0. Are you running this script on a different platform than before? I’m surprised your original code, https://github.com/pydata/xarray/issues/2450#issuecomment-426346137, didn’t raise the same error.