pprint - low width overrides depth folding

[iansedano]

BPO	45611
Nosy	@iansedano

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-10-26.07:40:20.607>
labels = ['type-bug', 'library', '3.10']
title = 'pprint - low width overrides depth folding'
updated_at = <Date 2021-10-26.07:40:20.607>
user = 'https://github.com/iansedano'

bugs.python.org fields:

activity = <Date 2021-10-26.07:40:20.607>
actor = 'iansedano'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-10-26.07:40:20.607>
creator = 'iansedano'
dependencies = []
files = []
hgrepos = []
issue_num = 45611
keywords = []
message_count = 1.0
messages = ['405027']
nosy_count = 1.0
nosy_names = ['iansedano']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45611'
versions = ['Python 3.10']

Linked PRs

• gh-89774: Fix pprint ignoring the depth limit at small width #153157

[iansedano]

Reproducible example:

>>> from pprint import pprint
>>> data = [["aaaaaaaaaaaaaaaaaa"],[2],[3],[4],[5]]
>>> pprint(data)
[["aaaaaaaaaaaaaaaaaa"], [2], [3], [4], [5]]

>>> pprint(data, depth=1)
[[...], [...], [...], [...], [...]]

>>> pprint(data, depth=1, width=7)
[[...],
 [...],
 [...],
 [...],
 [...]]

>>> pprint(data, depth=1, width=6)
[['aaaaaaaaaaaaaaaaaa'],
 [2],
 [3],
 [4],
 [5]]

The depth "folds" everything deeper than 1 level. Then if you lower the width of the output enough, what was once on one line, will now be split by newlines.

The bug is, if you lower the width below seven characters. Which is the length of [[...], It seems to override the depth parameter and print the everything with no folding. This is true of deeply nested structures too.

Expected behavior: for the folding ... to remain.

Why put the width so low?

I came across this because of the behavior of compact:

By default, if a data structure can fit on one line, it will be displayed on one line. compact only affects sequences that are longer than the given width.

**There is no way to force compact as False for short items**, so as to make sure all items, even short ones, appear on their own line.

[1,2,3] - will always appear on its own line, there is no way to make it appear like:

[1,
2,
3]

The only way is by setting a very low width.