I think the idea you're looking for is an alternative for the pprint module that allows classes to have formatting hooks that get passed in some additional information (or perhaps a PrettyPrinter object) that can affect the formatting.

This would seem to be an ideal thing to try to design and put on PyPI, *except* it would be more effective if there was a standard, rather than several competing such modules, with different APIs for the formatting hooks.

So I encourage having a discussion (might as well be here) about the design of the new PrettyPrinter API.

On Sun, Mar 15, 2020 at 4:08 AM Steve Jorgensen <stevej@stevej.name> wrote:

This is really an idea for an idea. I'm not sure what the ideal dunder method names or APIs should be.

Encoding awareness:

The informal (`str`) representations of `inf` and `-inf` are "inf" and "-inf", and that seems appropriate as a known-safe value, but if we're writing the representation to a stream, and the stream has a Unicode encoding, then those might prefer to represent themselves as "∞" and "-∞". If there were a dunder method for informal representation to which the destination stream was passed, then the object could decide how to represent itself based on the properties of the stream.

Prettiness awareness:

It would be nice if an object could have control of how it is represented when pretty-printed. If there is any way for that to be done now, it is not at all evident from the pprint module documentation. It would be nice if there were some method that, if implemented for the object, would be used to allow the object to tell the pretty printer to treat it is a composite with starting text, component objects, and ending text.

Additional thoughts & open questions:

Perhaps there should only be stream awareness for informal representation and prettiness awareness for formal representation (separate concepts and APIs) or perhaps both ideas are applicable to both kinds of representation.

Is it better for a stream-aware representation method to return the value to be written to the stream or to directly append its representation to that stream?
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