On Apr 6, 2020, at 09:22, Dan Cojocaru firstname.lastname@example.org wrote:
Addressing your last concern, about __json__ being only class -> JSON, not JSON -> class, classes implementing __str__ only go class -> str, not str -> class.
Sure, but str is inherently one-way. There’s no unambiguous mapping from human-readable text to data.
That’s not true for JSON; the entire point of it is data interchange. You expect to be able to dump an object, send it over the wire or store it to a file, load it (or even parse it in JS or ObjC or Go or whatever) and get back an equivalent object. It’s easy to come up with ways to build on top of JSON to interchange things like time points or raw binary strings or higher-level structured objects, but they require doing something on both the encode side and the decode side. Just being able to encode them to something human-readable is useless—if I encode a datetime object, I need to get back a datetime (or Date or NSDate or whatever) on the other end, not a str (or string or NSString or whatever) that a human could tell is probably meant to be a datetime but will raise an exception when I try to subtract it from now().
(Of course JSON isn’t perfect, as anyone who’s tried to interchange, say, int64 values discovers… but it’s good enough for many applications.)