SourceData interface

[takluyver]

An object representing one source, with several keys:

xgm = run['SPB_XTD9_XGM/DOOCS/MAIN']

'beamPosition.ixPos.value' in xgm  # Check for key
xgm_keys = xgm.keys()  # Find all (selected) keys
beam_x = xgm['beamPosition.ixPos.value']  # Get a KeyData object

Closes #55

[philsmt]

Thank you, loving this interface pattern. I'm definitely using KeyData much more than the classic interface already.

It's not strictly touch the code changed in this PR, but I feel the specific syntax here makes it even more natural to expect keys to work without the attached .value:

'beamPosition.ixPos.value' in xgm # Check for key

I realize this remains debatable whether a Karabo viewpoint is valid on files. I actually meant to discuss at some point a general strategy on how to handle this conundrum, but it creeps up here again. I understand if you prefer to postpone it as part of a bigger problem, though.

[takluyver]

Thanks; I think it makes sense to try to do something about .value here.

[takluyver]

OK, both key in sourcedata and sourcedata[key] should now allow control keys without the .value suffix.

Since run[source, key] and various methods like run.get_array() now go through the sourcedata object, this should indirectly mean that you can leave off .value in a whole lot of places. We still treat the name with .value as canonical, though, for e.g. sourcedata.keys().

[tmichela]

Nice 👍

can we make a quick mention in the documentation, maybe here?

[takluyver]

Yes, of course, good point!

[tmichela]

LGTM

[philsmt]

I'm sorry striking the same notch (this saying probably doesn't work in English), but what do you think about adding an optional flag here to collapse .value and .timestamp? Something like omit_suffix or collapse_value_and_timestamp.

While it might only be useful in generic programming, I could imagine it something people want to do with the output from this function, and it might be convenient to provide it.

[takluyver]

That seems reasonable enough. What about something that defaults to True for including both as separate keys, like inc_timestamps=False or value_and_timestamp=False?

[philsmt]

Sure, either way is fine with me!

[takluyver]

I've implemented it with inc_timestamps=False as the option to hide the timestamp/value suffixes. I'm not 100% convinced on that name if anyone has a better idea, though. It's ignored for instrument sources.

I've also used this option when listing keys in lsxfel, so you no longer see separate timestamp & value listed there.

[philsmt]

Thanks, LGTM!