support to_data\from_data for DictInterval

[Zagrebelin]

I suppose to "serialize" DictIntevals to the list of 2-tuples ( (left, lower, upper,right), item ).

[Zagrebelin]

I think I have to add some tests here.

[AlexandreDecan]

Thanks for your PR! I will have a look asap and provide some feedback :)

[AlexandreDecan]

First of all, thank you for your contribution. I see that the purpose of this PR is to provide an "easy way" to import and export IntervalDict instances to Python's built-in datatype.

However, I don't really understand why this would be part of the library given that one can, quite easily, re-use the fundamentals provided by the library to do so (for instance, I would expect an IntervalDict to be exported using {P.to_data(k, ...): v for k, v in intervaldict.items()} and to be imported using a similar approach, e.g. IntervalDict._from_items({P.from_data(k, ...): v for k,v in d.items()})). Could you elaborate a little bit on the need to include these routines into the library?

Thank you! ;-)

[Zagrebelin]

I using your library in my current project to handle time and datetime intervals of some events in Django application.
It was very easy with to_data\from_data and jsonfield.
Today i received a new task to store some extra information within intervals, and a IntervalDicts with time intervals as keys and dict as values are works very well for me. There are a routines for store Intervals to plain object, but there is nothing to store IntervalDict so i suggest this PR.

Yes, you are right. I submit a stupid non working code, it was my fault.

[AlexandreDecan]

It's not stupid at all ;-)

I was mainly wondering whether this should be part of the library or not.

[Zagrebelin]

As far we have a to_data/from_data for simple Intervals I think there should be dict_to_data. Just for unification.

But this is your library and your decision.

[AlexandreDecan]

Indeed, but the reason why we have from_data/to_data is simply because there is no easy alternative to offer a similar service than having these functions. What I mean is that an IntervalDict can be exported and imported the same way than any other dict in Python. The only "issue" would be to convert the keys (that are Interval objects) to something serializable, and that can be easily done with from_data/to_data.

The changes you made for 1674b17 show that it is easy to write such import/export without having to rely on some internals, that's why I'm hesitating to merge this PR.

[AlexandreDecan]

We have discussed a lot on whether we should bring this functionality to portion or not, and have concluded that we shouldn't. The IntervalDict class is mostly a convenient class to map data to intervals and, as such, is kind of a third-party feature of portion. If at some point, we decide to move IntervalDict to the main set of features, we'll reconsider our decision.

Thanks again for this PR, I'm sorry for its fate.