On Sat, Jul 25, 2020 at 1:18 AM Gábor Bernát <jokerjoke...@gmail.com> wrote:
>
> Hello, I'd like to bring to your attention
> https://bugs.python.org/issue41383. The core idea here is per Elizaveta
> Shashkova:
>
> I would like to have a lazy repr evaluation for the objects! Sometimes users
> have many really large objects, and when debugger is trying to show them in
> Variables View (=show their string representation) it can takes a lot of
> time. We do some tricks, but they not always work. It would be really-really
> cool to have parameter in repr, which defines max number of symbols we want
> to evaluate during repr for this object.
> Maybe repr is not the best here, because that should be interpreter
> meaningful, but instead the __str__ method that's better for this. Maybe we
> could pass in an optional limit argument to these methods, so that the user
> can decide what to print depending on how many characters he has left?
>
I honestly don't think that either __repr__ or __str__ is appropriate
for this. You need some sort of hook that has, potentially, a lot of
debugger hooks in it. I would say it's best handled by some sort of
multiple dispatch within the debugger itself; it can handle core data
types (list/tuple, dict) and then provide hooks for custom types to
register themselves with it.
But one thing that would be kinda nice would be to have a way for a
class to say "I'm like a dict, but with extra info". Consider
defaultdict and Counter:
>>> c = collections.defaultdict(list)
>>> c[1].append("asdf")
>>> c
defaultdict(<class 'list'>, {1: ['asdf']})
>>> collections.Counter("Hello, world")
Counter({'l': 3, 'o': 2, 'H': 1, 'e': 1, ',': 1, ' ': 1, 'w': 1, 'r':
1, 'd': 1})
Both of them include a dict-like repr in their reprs, and both of them
would probably want to have the debugger display them in a dict-like
way too.
Maybe reprlib would be the place for something like this?
ChrisA
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