The problem is we do not know what your real goal is in regards to when this data is to be used.
Same session, same day, some other day. Or even some other computer/location.
So to answer where or even how best to save/store the data is hard to answer without that.
I think json is in any case the best way to go. There are a few threads ( if you do a search) on how to write out or read json from a file.
Here is one for example along ( if I remember correctly a video explaining more on the concept )