`pprint(..., expand=True)`'s "best effort" for adhering to `width=...` seems not very "best"

[asottile]

Feature or enhancement

Proposal:

was playing around with this both for a pytest improvement and for a video -- and noticed that the width setting doesn't seem to play all that well with expand=True -- perhaps the width calculation is actually based on the old algorithm? (haven't looked closely yet)

import pprint

obj = {'a' * 12: 1, 'b' * 20: 2, 'c' * 30: {'d' * 5: 3, 'e' * 40: 3}}

pprint.pprint(obj)
print('===')
pprint.pprint(obj, expand=True)

this is the current output on an 80 character terminal (I've added newlines where natural wrapping occurs in the terminal)

$ python3.15 t.py 
{'aaaaaaaaaaaa': 1,
 'bbbbbbbbbbbbbbbbbbbb': 2,
 'cccccccccccccccccccccccccccccc': {'ddddd': 3,
                                    'eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee': 
3}}
===
{
 'aaaaaaaaaaaa': 1,
 'bbbbbbbbbbbbbbbbbbbb': 2,
 'cccccccccccccccccccccccccccccc': {'ddddd': 3, 'eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
eeeeeeee': 3},
}

it makes sense to me that the old format doesn't line break properly (it wouldn't fit with the 36-space (!) indent -- but I believe the new format should be able to do better -- something similar to:

{
 'aaaaaaaaaaaa': 1,
 'bbbbbbbbbbbbbbbbbbbb': 2,
 'cccccccccccccccccccccccccccccc': {
  'ddddd': 3,
  'eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee': 3,
 },
}

(which is well within the width=80 constraint)

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

I believe this is also related to #149189 -- and perhaps would strengthen the ideas in that issue if resolved

Linked PRs

• gh-155596: Fix pprint expand mode ignoring width for nested values #155926

[cobed95]

@corona10 @hugovk Hi PyCon KR 2026 CPython Sprint mentors, I would be honoured to work on this in tomorrow's sprint.
If you think that this issue is not appropriate for the sprint, please let me know and I'll look for another one.

Thank you.