gh-112632 : Added an option for block formatting to ``pprint`` by StefanTodoran · Pull Request #129274 · python/cpython

StefanTodoran · 2025-01-25T02:34:00Z

Adds a block print option to pprint. This option is not compatible with compact. Although the original issue only mentions dictionaries, this implementation implements block style for every datastructure supported by pprint. I've been testing it with the code in this gist, which is just a bunch of random datastructures filled with dummy data.

Issue: pprint with compact indent #112632

ghost · 2025-01-25T02:34:02Z

All commit authors signed the Contributor License Agreement.

bedevere-app · 2025-01-25T02:34:07Z

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

donbarbos · 2025-02-05T23:01:15Z

looks pretty good 👍, but

I think you can move test cases from your gist to Lib/test/test_pprint.py.
It is also important to update documentation, you'll find them here Doc/library/pprint.rst.

And please try to make sure CI passes

bedevere-app · 2025-02-06T23:35:52Z

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

bedevere-app · 2025-02-06T23:43:40Z

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

bedevere-app · 2025-02-07T00:14:10Z

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

donbarbos · 2025-02-07T00:23:08Z

Could you also add a News entry into the Misc/NEWS.d (check bedevere's comments)?

And I think it's a full fledged new feature so this update deserves to be in Doc/whatsnew/ (What's New entry)

StefanTodoran · 2025-02-07T00:39:41Z

I've added a test case for the new block_style parameter and updated the documentation. Will add the news entry now. Quick question:

How can I make the CI pass? I've only changed Lib.pprint.py and I pass Lib/test/test_pprint.py, so I don't understand why exactly the Tests / Thread sanitizer (free-threading) CI test is failing.

donbarbos · 2025-02-07T00:46:30Z

How can I make the CI pass? I've only changed Lib.pprint.py and I pass Lib/test/test_pprint.py, so I don't understand why exactly the Tests / Thread sanitizer (free-threading) CI test is failing.

sometimes the problem may not be in you and you need to wait and update your branch (at least it helped me)

Misc/NEWS.d/next/Library/2025-02-07-00-48-07.gh-issue-112632.95MM0C.rst

Doc/library/pprint.rst

Lib/test/test_pprint.py

donbarbos · 2025-02-09T11:30:43Z

and don't forget to add news to Doc/whatsnew/3.14.rst

And I think it's a full fledged new feature so this update deserves to be in Doc/whatsnew/ (What's New entry)

Co-authored-by: donBarbos <[email protected]>

StefanTodoran · 2025-02-25T17:02:44Z

I've merged those changes. Thanks for helping me out with that! Is there anything else?

donbarbos · 2025-02-25T17:09:44Z

I've merged those changes. Thanks for helping me out with that! Is there anything else?

Let's try to solve problems with test_pprint.QueryTestCase.test_block_style

Lib/test/test_pprint.py

Co-authored-by: donBarbos <[email protected]>

donbarbos · 2025-02-26T16:47:42Z

I think we can ping @tomasr8 if you're done making changes.

StefanTodoran · 2025-02-26T19:19:53Z

Sounds good, I have no more changes to add.

tomasr8

I think it's looking pretty good now! Just two comments:

Doc/whatsnew/3.14.rst

tomasr8 · 2025-02-26T20:42:25Z

Lib/pprint.py

-        stream.write(cls.__name__ + '({')
-        if self._indent_per_level > 1:
+        stream.write(self._format_block_start(cls.__name__ + '({', indent))
+        if self._indent_per_level > 1 and not self._block_style:


This is not covered by tests (the condition is always False).

For such a large change, I suggest running coverage and checking the html report to make sure your tests cover all cases. There's a guide here, but the gist is:

./python -m ensurepip ./python -m pip install coverage ./python -m coverage run --pylib --source=pprint Lib/test/regrtest.py test_pprint ./python -m coverage html -i --include=`pwd`/Lib/* --omit="Lib/test/*,Lib/*/tests/*"

I don't understand, what do you mean the case is not covered? The existing tests already covered the case where _block_style is False and _indent_per_level is >1.

Also when I run the coverage command I don't see anything missing, am I doing something wrong?

python3 -m coverage run --pylib --source=pprint Lib/test/regrtest.py test_pprint /Users/stodoran/Desktop/cpython/venv/lib/python3.13/site-packages/coverage/inorout.py:486: CoverageWarning: Already imported a file that will be measured: /opt/homebrew/Cellar/[email protected]/3.13.2/Frameworks/Python.framework/Versions/3.13/lib/python3.13/pprint.py (already-imported) self.warn(msg, slug="already-imported") Using random seed: 4261013096 0:00:00 load avg: 4.87 Run 1 test sequentially in a single process 0:00:00 load avg: 4.87 [1/1] test_pprint == Tests result: SUCCESS == 1 test OK. Total duration: 129 ms Total tests: run=44 Total test files: run=1/1 Result: SUCCESS

python3 -m coverage html -i --include=`pwd`/Lib/* --omit="Lib/test/*,Lib/*/tests/*" No data to report.

From what I can see it's not covered:

I think there's some issue with the coverage command you ran as it says:

No data to report.

Try running it with the compiled binary directly, not with some other system python.

@StefanTodoran if you can't get HTML-based report you can use cli:

$ ./python -m coverage report --show-missing Name Stmts Miss Branch BrPart Cover Missing ----------------------------------------------------------- Lib/pprint.py 476 81 182 7 87% 37-46, 57, 67-72, 77, 82, 87-99, 102, 110, 115-116, 172, 174-177, 182, 185, 189, 192-195, 220, 226, 232, 243-245, 262-264, 276-278, 284-286, 293-295, 312-315, 353->326, 367-369, 388-390, 400-402, 409-411, 424-426, 444, 464, 507, 513, 516, 523, 537-539, 546, 556-558, 560-561, 573-575, 595-597, 600-602, 605-607, 610-612, 694, 703, 717->exit ----------------------------------------------------------- TOTAL 476 81 182 7 87%

I don't know why on the main branch this line is shown as covered, but this can be solved by adding an explicit pass of indent>1 to the QueryTestCase.test_counter test, like this:

d = collections.Counter('senselessness') self.assertEqual(pprint.pformat(d, indent=2, width=1), """\ Counter({ 's': 6, 'e': 4, 'n': 2, 'l': 1})""")

and the line will become covered 👍
(unfortunately i can't send you a suggestion as there is no diff nearby, so please add it yourself)

lordmauve · 2025-03-25T11:03:46Z

Lib/pprint.py

-        stream.write('[')
+        stream.write(self._format_block_start('[', indent))
        self._format_items(object, stream, indent, allowance + 1,
                           context, level)
-        stream.write(']')
+        stream.write(self._format_block_end(']', indent))


You have a lot of repeated code here conditional on self._block_style. How about defining a context manager to clean this up?

with self._block(stream, indent, '[', ']') as new_indent: self._format_items(object, stream, new_indent, allowance + 1, context, level)

AA-Turner · 2025-04-20T22:28:55Z

Doc/library/pprint.rst

+                 compact=False, sort_dicts=False, underscore_numbers=False, \
+                 block_style=False)


These are keyword-only (after *), so we have the luxury of alphabetical sorting:

Suggested change

compact=False, sort_dicts=False, underscore_numbers=False, \

block_style=False)

block_style=False, compact=False, sort_dicts=False, \

underscore_numbers=False)

AA-Turner · 2025-04-20T22:29:53Z

Doc/library/pprint.rst

+                     compact=False, sort_dicts=True, \
+                     underscore_numbers=False, block_style=False)


Likewise

Suggested change

compact=False, sort_dicts=True, \

underscore_numbers=False, block_style=False)

block_style=False, compact=False, \

sort_dicts=True, underscore_numbers=False)

AA-Turner · 2025-04-20T22:30:57Z

Doc/library/pprint.rst

+      If ``True``,
+      opening parentheses and brackets will be followed by a newline and the
+      following content will be indented by one level, similar to block style
+      JSON formatting. This option is not compatible with *compact*.


This option is not compatible with compact.

A passing thought: Perhaps introduce a mode (str) argument, and deprecate compact in favour of it? It's not great to have two conflicting Booleans, though it may be the best option for now.

AA-Turner · 2025-04-20T22:31:31Z

Doc/library/pprint.rst

+                      compact=False, sort_dicts=True, \
+                      underscore_numbers=False, block_style=False)


Likewise

Suggested change

compact=False, sort_dicts=True, \

underscore_numbers=False, block_style=False)

block_style=False, compact=False, \

sort_dicts=True, underscore_numbers=False)

AA-Turner · 2025-04-20T22:32:00Z

Doc/library/pprint.rst

+                         compact=False, sort_dicts=True, \
+                         underscore_numbers=False, block_style=False)


Likewise

Suggested change

compact=False, sort_dicts=True, \

underscore_numbers=False, block_style=False)

block_style=False, compact=False, \

sort_dicts=True, underscore_numbers=False)

AA-Turner · 2025-04-20T22:33:39Z

Lib/pprint.py

+                 compact=False, sort_dicts=True, underscore_numbers=False,
+                 block_style=False):


Suggested change

compact=False, sort_dicts=True, underscore_numbers=False,

block_style=False):

block_style=False, compact=False, sort_dicts=True,

underscore_numbers=False):

AA-Turner · 2025-04-20T22:34:26Z

Lib/pprint.py

+            pretty-printed json.dumps() when `indent` is supplied. Incompatible
+            with compact mode.


Suggested change

pretty-printed json.dumps() when `indent` is supplied. Incompatible

with compact mode.

pretty-printed json.dumps() when ``indent`` is supplied.

Incompatible with compact mode.

AA-Turner · 2025-04-20T22:35:43Z

Lib/pprint.py

+        else:
+            return start_str


Suggested change

else:

return start_str

return start_str

AA-Turner · 2025-04-20T22:35:52Z

Lib/pprint.py

+        else:
+            return end_str


Suggested change

else:

return end_str

return end_str

AA-Turner · 2025-04-20T22:36:19Z

Lib/pprint.py


        cls_name = object.__class__.__name__
-        indent += len(cls_name) + 1
+        indent += len(cls_name) + 1 if not self._block_style else self._indent_per_level


Please keep to 79/80 characters (PEP 8)

donbarbos · 2025-05-31T09:36:52Z

@StefanTodoran I think your PR is useful, maybe you can tell if you'll continue working and if so when you can continue working

StefanTodoran · 2025-06-01T19:35:18Z

@donbarbos Sorry about the radio silence, due to work responsibilities my bandwidth is too limited to devote time to this change right now. I can give access to my fork of the repo if someone wants to pick up where I left off.

donbarbos · 2025-06-03T08:37:50Z

@donbarbos Sorry about the radio silence, due to work responsibilities my bandwidth is too limited to devote time to this change right now. I can give access to my fork of the repo if someone wants to pick up where I left off.

thanks, i will be glad to finish this work. but as far as i know the usual practice is to open a new PR, so i can fork your branch and send a new PR to be able to control the PR discussion

hugovk · 2026-03-28T14:33:46Z

Closing in favour of #136964, thanks all.

Added an option for block formatting to pprint

b9baf94

bedevere-app bot added the awaiting review label Jan 25, 2025

bedevere-app bot mentioned this pull request Jan 25, 2025

pprint with compact indent #112632

Open

tomasr8 self-requested a review January 25, 2025 09:29

Small bug fix for indent=1, added to unit test

f5fcbfc

Merge branch 'main' into fix-issue-112632

31a4d1e

Remove set from block style unit test (since order kept changing)

a92ef3d

blurb-it bot and others added 3 commits February 7, 2025 00:48

📜🤖 Added by blurb_it.

d9a147f

Merge branch 'main' into fix-issue-112632

ffef3b0

Fix params in news entry

19e4e08

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Fix line length for news entry

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StefanTodoran added 2 commits February 6, 2025 17:58

Shorten news entry

c446aa1

Merge branch 'main' into fix-issue-112632

f9bd6ef

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StefanTodoran added 3 commits February 19, 2025 10:23

Address documentation related PR comments

49b1108

Merge branch 'main' into fix-issue-112632

62dd5e5

Fix length of title underline :/

0b8fd2b

StefanTodoran and others added 10 commits February 25, 2025 08:49

Update Lib/pprint.py

5abab85

Co-authored-by: donBarbos <[email protected]>

Update Lib/pprint.py

5e8a624

Co-authored-by: donBarbos <[email protected]>

Update Lib/test/test_pprint.py

5ffbd0d

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Update Lib/test/test_pprint.py

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Update Lib/test/test_pprint.py

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Co-authored-by: donBarbos <[email protected]>

Update Lib/test/test_pprint.py

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Co-authored-by: donBarbos <[email protected]>

Update Lib/test/test_pprint.py

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Update Lib/test/test_pprint.py

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Update Lib/test/test_pprint.py

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StefanTodoran added 3 commits March 27, 2025 18:21

Split large test case into multiple smaller ones, update news entry

37312d9

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AA-Turner changed the title ~~gh-112632 : Added an option for block formatting to Lib/pprint.py~~ gh-112632 : Added an option for block formatting to pprint Apr 20, 2025

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donbarbos mentioned this pull request Jul 22, 2025

gh-112632: Add optional keyword-only argument expand to pprint #136964

Open

hugovk closed this Mar 28, 2026

		compact=False, sort_dicts=False, underscore_numbers=False, \
		block_style=False)

		compact=False, sort_dicts=True, \
		underscore_numbers=False, block_style=False)

		compact=False, sort_dicts=True, underscore_numbers=False,
		block_style=False):

		pretty-printed json.dumps() when `indent` is supplied. Incompatible
		with compact mode.

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