I think Python's distinction between code (e.g. classes) and data (e.g. dicts) is a good distinction to keep -- if you want code, define code, and datcalasses make that very easy these days.
> This feature is far more useful in JS because JS objects double up as mappings -
Exactly. And because of this the behaviour is well defined. However, I think that there's alway as issue with "data", e.g. mappings, and "code", e.g. classes with attributes.
Given how dynamic Python is, it can be a fuzzy boundary, but I don't think we should make it even fuzzier. (and it JS, there is no boundary at all).
Using Chris's example:
for {codec_type, width, height} in info["streams"]:
if codec_type == "video":
...
This would be extremely convenient, and it doesn't really work with dataclasses.
First, how does this work now? This?
for stream in info["streams"]:
if stream['codec_type'] == "video":
....
Is that so bad? as you have hard_coded codec_type, I suppose it's a bit more kludgy, but if the codec_type was in a variable, it would be more convenient.
As for dataclasses, this is what i mean by "code" vs "data" -- if you know when you are writing the code exactly what key (fields, etc) you expect , and you want to be able to work with that data model as code (e.g. attribute access, maybe some methods, then you do:
In [10]: @dataclass
...: class Stream:
...: codec_type : str
...: width: int
...: height: int
And if you have that data in a dict (say, from JSON, then you can extract it like this:
In [11]: stream_info = {'codec_type': 'video',
...: 'width': 1024,
...: 'height': 768,
...: }
In [12]: stream = Stream(**stream_info)
In [13]: stream
Out[13]: Stream(codec_type='video', width=1024, height=768)
That only works if you dict is in exactly the right form, but that would be the case anyway.
Granted, that's a lot of code for a quickscript, but if it's a quick script, just work with the dict.
IN practice, it's not so simple when you have a more nested data structure, but I don't think this proposal would help with that, and it's not hard to build that on top of dataclasses either, see Pydantic, or attrs, or my own half-baked flexi project:
(note: half-baked because the public project is not well tested nor documented, but I am using this very code in a pretty substantial system with a very highly nested structure:
-CHB