Supporting datetime.timedelta and np.timedelta64 in parcels' arguments

[VeckoTheGecko]

Python offers two different types of timedelta objects - datetime.timedelta and numpy.timedelta64.

From a public facing API POV, I think it would be good to be able to support both of these types for the params:

• outputdt in ParticleFile
• runtime, dt in ParticleSet.execute

From what I can tell ¹, I think we should convert these under the hood to a numpy timedelta object for use internally.

Supporting both in the public API allows runtime=timedelta(days=2, hours=2) which I think is nice API from a user POV.

Footnotes

1. I still need to work out exactly the motivation and workings of numpy datetime/timedelta objects (link) ↩

[VeckoTheGecko]

Supporting both in the public API allows runtime=timedelta(days=2, hours=2) which I think is nice API from a user POV.

To elaborate, say a user wants have specific runtime of 1 day and 12 hours. They can do that via:

runtime = datetime.timedelta(days=1, hours=12)

rather than having to use numpy:

runtime = np.timedelta64(1, "D") + np.timedelta64(12, "h")
# or
runtime = np.timedelta64(36, "h")

[erikvansebille]

This was fixed in #2142