[Python-ideas] Json object-level serializer

Cameron Simpson cs at zip.com.au
Sat Jul 31 07:59:12 CEST 2010

I'm uncomfortable with the __foo__ style proposed. Details and "what I
would do" below.

On 30Jul2010 12:06, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
| Mike Graham wrote:
| >Since there isn't really any magic going on, why use a __foo__ name?
| >The majority of __foo__ names are for things you shouldn't reference
| >yourself
| To my mind, the main reason is to avoid name clashes. Protocol
| methods often may need to be added to just about any class,
| and using a __foo__ name greatly reduces the chance of it
| coinciding with some pre-existing class-specific method.

Might not the adder of a class specific method make the same argument?
If they really want a class _specific_ method, ought thy not to be using
the __foo style, thus avoiding clashes anyway?

The __json__ name make me uncomfortable; to my mind __foo_ names belong
to the language in order to implement/override stuff like [], not to a
library hook.

| Anyway, you don't call it yourself in this case either -- it's
| called by the proposed json-serialising framework.

I'm curious; what's the special benefit to JSON here? I don't mean JSON
is unpopular or horrible, but I can see people going to a __xml__ hook
for a proposed XML serialisation framework, and __sql__ for db storage,
and ...

I'm doing a little serialisation myself for another purpose. My code
gets classes that want serialisation to register themselves with the
serialisation module thus:

  # DB is a NodeDB instance, which can store various objects
  DB.register_type(class, tobytes, frombytes)

where class is the class desiring special serialisation and tobytes and
frombytes are callables; tobytes takes an instance of the class and
returns the byte serialisation and frombytes does the reverse.

No special names needed and no __foo__ special name reservation.

Why wouldn't one just extend the json module with a "serialise this"
and "unserialise this" type registry?

Cameron Simpson <cs at zip.com.au> DoD#743

You can listen to what everybody says, but the fact remains that you've got
to get out there and do the thing yourself.     - Joan Sutherland

More information about the Python-ideas mailing list