Template function to offset datetime parameter

[leifdenby]

I have a opendap server where the files are stored with a time-span in the filename which is always one hour apart, for example
LIDAR_obs_09291300_09291400.nc
i.e. the format is
LIDAR_obs_{{t_start.strftime("%m%d%H%M")}}_{{t_end.strftime("%m%d%H%M")}}.nc

It would be nice to have the user just provide t_start (which I can then check for validity) and then calculate t_end from it (t_end = t_start + datetime.timedelta(hours=1)). I appreciate that allowing for custom functions would open a whole can of worms, but maybe adding a specialised jinja template function for offsetting datetimes might be useful?

I've created one called offset_datetime, with that the above URL can be written as:
LIDAR_obs_{{t_start.strftime("%m%d%H%M")}}_{{offset_datetime(t_start, hours=1).strftime("%m%d%H%M")}}.nc

Would this be something you would consider adding to intake?

[martindurant]

I am personally uncertain. I can see the benefit, obviously - and indeed there could be many other utility functions that might be handy. I'm not sure how one would go about specifying the set to include - we would not generally want to allow arbitrary code execution during template filling.

Perhaps you could tag one or two of the maintainers on intake-xarray to see if someone else already has a solution for this kind of thing or has thoughts on it.