Improving pretty-printing in Python

divbzero — Sat, 21 Mar 2020 07:22:17 +0000

I don’t have a strong opinion on this, but would note that the debate over a __pretty__ method seems to parallel the debate over a __json__ method. [1] [2]

[1]: https://bugs.python.org/issue27362

[2]: https://mail.python.org/pipermail/python-ideas/2010-July/...

__json__ has not gained traction, probably because JSON serialization can be application dependent and JSONDecoder already provides a flexible way to customize JSON serialization.

__pretty__ seems even more in the eye of the beholder so I’m not surprised to see hesitant reactions to the idea.

Improving pretty-printing in Python

NYKevin — Thu, 19 Mar 2020 01:19:02 +0000

If you want to do this "at the level of application I/O," I would tend to assume you'd just subclass reprlib.Repr and implement the repr_foo() method overrides. Since that's already in the standard library, I'm not sure I understand what they are proposing... Maybe you could add a fallback option where reprlib.Repr.repr1() dispatches to some dunder method on the object (with the expectation that the object call back into repr1() when it wants to format a subobject)? That seems messy, since I usually think of dunder methods as belonging to the language rather than the standard library. But there is precedent for this sort of thing (e.g. __copy__ and __deepcopy__), so I suppose it could work.

LWN: Comments on "Improving pretty-printing in Python"

Improving pretty-printing in Python

Improving pretty-printing in Python