ENH: Drop Pandas as dependency about rocketry

[Miksus]

Working on this and making some great progress. This was easier than I thought and managed to replicate timedelta parsing quite fine (should not break anything unless you have used really odd strings).

I think we could replace pd.Timestamp with python-dateutil which has quite OK datetime parser.

[Miksus]

It seems three things need to be somewhat replaced that are currently used from Pandas:

• pd.Interval (used in redengine/core/time/base.py & redengine/core/time/interval.py)
• pd.Timedelta (used redengine/session.py, redengine/core/task.py, multiple places in redengine/time)
• pd.Timestamp (used in redengine/pybox/query/base.py, redengine/core/time/base.py & redengine/core/time/interval.py)

Interval could be replaced with a simple custom class or so. I think it is used only to check if a time is inside the interval (after or equal to left, before or equal to right). Seems Pandas' solution is in Cython but I don't think this is a performance matter.

Timedelta is probably the hardest bit. We need a better timedelta parser than provided by most libraries. Possibly creating one own to make it work exactly right. Pandas' solution is in Cython but it probably complicates building if it is directly copied. Seems the parsing is possibly here pandas/_libs/tslibs/timedeltas.pyx

Timestamp There might be some places where a string can be passed and parsed. Perhaps dateutil could be an option.

[gaby]

👍🏻 for removing both Pandas and Numpy. These dependencies dont play well with Alpine and require compiling them to use them.

[gaby]

Great to hear!