dvc: metrics.show() and params.show() order

[Suor]

It looks like these go in somewhat random order. Is it possible to make them reflect the order in dvc.yaml file? Since Python 3.6 dicts preserve order so we can still use that as an output type.

[efiop]

@Suor Could you elaborate why that even matters?

[Suor]

To use as a default order of columns in the viewer. Sure we can simply sort alphabetically, but the order in a file is probably user defined already and then we should use it.

[efiop]

That seems really viewer-specific. Not sure if it is worth adopting as dvc core behavior. Have you implemented it in the viewer already?

[efiop]

Ok, had a private discussion about it. So this matters for dvc CLI as well, so it is our problem too, though not as urgent. We don't have capacity to deal with it right now ourselves, so if it can be implemented in viewer for now or you could contribute the change back (at least for API) - that would be great.

[Suor]

Can't be implemented in the viewer (without monkey patching). So no not implemented yet in any way.

[dmpetrov]

It is important in CLI as well. It is hard to use with real-life files with dozens of metrics or params.

We should assume that users pay a lot of attention to order items inside the files and reuse it.

ToDo:

• preserve order in metrics: dvc metrics diff/show
• preserve order in params: dvc params diff/show

[Suor]

Implementation/API note: don't need to use OrderedDict in Python 3.6+, order is stable for dict too.

[auvipy]

Implementation/API note: don't need to use OrderedDict in Python 3.6+, order is stable for dict too.

Changed in version 3.7: Dictionary order is guaranteed to be insertion order. This behavior was an implementation detail of CPython from 3.6.

[skshetry]

This behavior was an implementation detail of CPython from 3.6.

@auvipy, the behaviour is very much unlikely to change. So, we can depend on it (we already do on a lot of places).