Would you generate a schema from the type annotations so that other languages can use the data?
JSON is really not the most efficient data representation for round-tripping to and from Python. A binary format (or pickle without arbitrary code execution) would solve for Python object > file > Python object. IMHO, JSON is most useful when the data needs to be read/written from (browser-side) JS, too. And then you need data validation for user-supplied input (which is not distinct from the deserialization problem). E.g. DRF has data validation. But (mypy) type annotations are insufficient for data validation: compare JSONschema and the maximum amount of information storable in mypy-compatible type annotations, for example. Data validation needs to return errors in a feedback loop with the user, so it's sort of more than just the preconditions that need to be satisfied before a function proceeds. - serialization from Python (TA useful) - deserialization with the same Python code (TA useful) - deserialization with other Python code (insufficient) - deserialization with other languages (insufficient) - form generation (insufficient) - data validation (insufficient) - preconditions (insufficient) So, IMHO type annotations are not insufficient and thus redundant and not elegant. On Tue, Apr 7, 2020, 11:45 AM Tin Tvrtković <tinches...@gmail.com> wrote: > As the author of one of these third-party libraries, I feel like I can > contribute to this discussion. It can indeed be done very elegantly with > type annotations, and it should for sure be left to the ecosystem. > > The only things we need from core Python are good tools for dealing with > run-time type information. For example, singledispatch doesn't really work > with types (i.e. Optionals, Unions, Sequences as opposed to actual > classes), but all of that can be worked around. > > In my experience, runtime type information is extremely useful exactly in > cases of deserialization, and for big projects starts being useful much > before the type information starts being useful in a static analysis > context. > > >> From: Greg Ewing <greg.ew...@canterbury.ac.nz> >> Subject: [Python-ideas] Re: Improvement: __json__ >> To: python-ideas@python.org >> Message-ID: <e70016ba-5419-e252-d7bd-9705dbebf...@canterbury.ac.nz> >> Content-Type: text/plain; charset=utf-8; format=flowed >> >> On 7/04/20 4:57 am, Wes Turner wrote: >> > Python object > JSON > object requires type information to be >> serialized. >> >> Not necessarily -- Java's json library uses reflection on compile >> time type information to deserialise json into an object hierarchy. >> You tell it the class corresponding to the top level and it figures >> out the rest. >> >> Something similar could be done in Python using type annotations. >> >> -- >> Greg >> >> _______________________________________________ > Python-ideas mailing list -- python-ideas@python.org > To unsubscribe send an email to python-ideas-le...@python.org > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > Message archived at > https://mail.python.org/archives/list/python-ideas@python.org/message/ISSUQVYI5OYYXKELUNCD5YCEDZ75LCEB/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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