Ned Batchelder

Python, software, coverage.py, typography, juggling, Boston, autism (dad). Laughing at the world doesn't mean I don't take it seriously. He/him.

Public Key

npub18sd9m0yzelqj7e0khk0zs0t3h49x789g2djqvek06hy9vqmcq6cs0t83tx

NIP-05 Address

nedbat@hachyderm-io.mostr.pub

Profile Code

nprofile1qqsrcxjahjpvlsf0vhmtm83g84cm6jn0rj59xeqxvm8atjzkqduqdvgpz3mhxue69uhhyetvv9ujuerpd46hxtnfduqs6amnwvaz7tmwdaejumr0dsmljzgh

Publishing to

relay.damus.io

nos.lol

Author Public Key

npub18sd9m0yzelqj7e0khk0zs0t3h49x789g2djqvek06hy9vqmcq6cs0t83tx

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Last Notes

2026-10-22 16:35:55 UTC

A new release of coverage․py today with a ton of fixes: https://pypi.org/project/coverage/7.17.0 Also drops 3.10 support.
And, one of the more interesting changelog entries:
> Kept the political banner in the README. Closes issue 2344: https://github.com/coveragepy/coveragepy/issues/2344

2026-09-18 13:07:15 UTC

More about my lightning talk from #PyConUS2026: it's hard for me to remember to keep quiet too!
https://nedbatchelder.com/blog/202609/silence_is_golden_lightning_talk

2026-08-23 19:48:21 UTC

In the #Python Discord, someone was trying to understand how Python code is executed without ever being turned into native CPU instructions. So I wrote a tiny programming language compiling to bytecodes. 300 lines of Python.
https://nedbatchelder.com/blog/202608/micro_language_implementation_calcium

2026-08-09 21:40:00 UTC

A simple way to get caller-specific coverage measurement:
https://nedbatchelder.com/blog/202608/callerspecific_coverage
Would you use something like this?

2026-08-07 15:31:59 UTC

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@nprofile…4xpq Yes, I get why you mistrust Anthropic. I'm asking why you DO trust Open AI? You quote an Anthropic investor calling Dario a religious figure. I gave you Sam Altman alluding to himself as a religious figure.

2026-08-06 15:33:58 UTC

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@nprofile…4xpq I agree with your concerns about Anthropic, but I'm not sure why you single them out:
https://www.reddit.com/r/agi/comments/1cqsu4j/the_cult_vibe_of_sam_altman_explained_by_sam/
Sam Altman shared this quote:
"successful people create companies. more successful people create countries. the most successful people create religions."

2026-08-03 23:53:55 UTC

Very cool.
https://www.andrewt.net/dithered-qr-codes/
https://media.hachyderm.io/media_attachments/files/117/034/269/660/944/343/original/668ed8259b6b8d11.png

2026-07-25 20:10:55 UTC

Because someone in the #Python Discord was asking about structuring tests alongside their project code, I added a bit of test structure to my pkgsample explainer: https://github.com/nedbat/pkgsample

2026-07-23 17:47:01 UTC

Python packages should explicitly declare their version support with PyPI classifiers. https://pyreadiness.org/3.13/ lists 90 packages that don't declare support for 3.13, when many of those packages do support it.
It's not hard to do, and it helps people understand what they can count on.

2026-06-29 16:25:16 UTC

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@nprofile…44dh Basically, LLMs are good enough at language that social engineering works against them.

2026-06-28 16:01:28 UTC

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@nprofile…q443 The two I've heard (and have seen) are "delve" and "whilst", so searching for those might turn up something.

2026-06-09 15:16:24 UTC

Boston Python is having a relaxed outdoor social event next Monday night June 15th. Come hang out! No presentations, no pressure. Any level of #Python interest (including None!) is welcome. Please boost to reach more techies in the #Boston area, thanks <3
https://www.meetup.com/bostonpython/events/315011438/

2026-05-27 17:00:50 UTC

Advice for new #Python learners: break the habit of starting every for loop with `for i in`: there is probably a much better name for your iteration variable than `i`.

2026-05-18 19:02:45 UTC

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@nprofile…yz28 Oddly, Canonical asks about your high school grades.

2026-05-16 21:48:31 UTC

Can you really claim to support recent Python versions if you don't have 3.16 in your CI matrix?
https://github.com/coveragepy/coveragepy/blob/main/.github/workflows/python-nightly.yml#L57-L58

2026-05-16 17:49:25 UTC

It's hard to express how great Pablo's keynote was. One for the ages (to over-extend his metaphor). #PyConUS
#nevent1q…kvsh

2026-04-30 16:33:52 UTC

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@nprofile…uvqd @nprofile…vlma Looking through it again, I don't see it specifically, but it definitely had the same feeling.

2026-04-30 15:03:04 UTC

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@nprofile…uvqd @nprofile…vlma I remember seeing output from Artspeak in https://www.amazon.com/Computer-Art-Jasia-Reichardt/dp/0289795508. I was endlessly fascinated by that book!

2026-04-26 17:12:17 UTC

"The background radiation of the internet"
https://arman-bd.hashnode.dev/i-left-port-22-open-on-the-internet-for-54-days-here-s-who-showed-up

2026-04-16 12:07:03 UTC

Next time someone says "C teaches you how computers really work" show them this: https://www.lighterra.com/papers/modernmicroprocessors/. None of this is visible from C (and most isn't visible from assembly).

2026-03-31 15:42:47 UTC

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@nprofile…4xpq Now I'm curious for more context for two reasons :)

2026-03-05 12:20:30 UTC

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@nprofile…4xpq @nprofile…zz66 I'm trying to understand what you're objecting to. The Anthropic response wasn't endorsing EA, it was talking about the good impulses and also pointing out the problems.

2026-02-25 21:42:28 UTC

The AI hype-cyclone is bad, but so is the anti-AI witch hunt. Commits co-authored by Claude do not mean that a project has "abandoned engineering as a serious endeavor"
Would we say that accepting contributions from new developers means we've "abandoned engineering as a serious endeavor"? No.
Claude can write wrong code. New contributors can write wrong code. What matters is what you do with that code after it's been written.

2026-02-25 19:59:55 UTC

Git won't track empty directories (because at heart it only tracks files). Common advice is to add a '.gitkeep' file so the directory isn't empty and git will make the directory.
EVEN BETTER ADVICE: put a README in the directory explaining what the empty directory is for and what will eventually be there.

2026-02-12 00:26:40 UTC

I promise I am not as crazy as this cover image makes me look:
https://www.youtube.com/watch?v=xjWjfRVTUHo

2026-01-25 23:19:28 UTC

Two nice things to add to your #Python testing toolkit.
https://nedbatchelder.com/blog/202601/testing_exceptions_and_caches

2025-11-30 21:45:53 UTC

Can you help me test a change to how coverage․py is packaged? It will take five minutes:
https://gist.github.com/nedbat/9b63b040cddd4778447cce21062d0843

2025-11-24 18:42:50 UTC

It's great that sites offer both light and dark mode, but why do I have to manually choose? Use `prefers-color-scheme` in your CSS, and the site will adjust to my already expressed preference: https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/At-rules/@media/prefers-color-scheme

2025-11-18 23:59:15 UTC

How much is your company spending to support the Python Software Foundation?
For comparison, how much do they spend on tips for expensed meals?
The PSF runs PyPI, where pip installs from. You depend on PyPI.
Fund the PSF. Tip your server!
https://www.python.org/psf/sponsorship/

2025-11-15 11:34:16 UTC

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@nprofile…59g0 I'm distracted by "why is MA north of NH?"

2025-11-05 18:45:02 UTC

Forget about trying to get your company to support something abstract like the PSF.
You use PyPI: you know, the place that pip installs from. Wouldn't it be bad if `pip install` stopped working? Support the organization that runs PyPI instead.
Surprise, it's the PSF! Support the PSF! Your company depends on #Python. You want it to keep working and keep being good.
Support the PSF. https://www.python.org/psf/sponsors/

2025-11-04 15:53:03 UTC

I got an email today thanking me for coverage․py and for fixing one issue in particular. They wanted to send me a hand-written note to my business address. I told them they didn't need to, but I really appreciated it. (I checked, it was not a scam..)
If you want to give back to open source, but can't make commits or give money, send a nice note. It has a bigger impact than you might think.

2025-10-27 19:52:04 UTC

Do you work for a company using Python? Is your company turning a profit? Show this blog post to coworkers and managers. Support the PSF!
https://hachyderm.io/@nedbat/115447331754295617

2025-10-27 17:34:43 UTC

Very very proud of the PSF choosing values over money. Far too rare these days. Glad to be part of an organization avoiding the craziness from Washington.
https://fosstodon.org/@ThePSF/115446659188615376

2025-10-15 15:21:25 UTC

Proud that coverage․py is the first top PyPI package to declare support for Python 3.15!
https://pyreadiness.org/3.15/
https://pypi.org/project/coverage/7.11.0/
https://media.hachyderm.io/media_attachments/files/115/378/873/554/841/370/original/84b70bb348c24845.png

2025-06-18 13:52:44 UTC

Forget tabs-vs-spaces and emacs-vs-vim. Today's question is:
assert expected == actual
or:
assert actual == expected
Explain your answer.

2025-06-16 11:00:14 UTC

Two geometric facts about 63, but how to connect them?
https://nedbatchelder.com/blog/202506/math_factoid_of_the_day_63.html

2025-06-06 16:32:54 UTC

Every June I dig this up:
https://hachyderm.io/@nedbat/110549139925182481

2025-05-30 01:32:54 UTC

Intriguing: https://css-doodle.com/

2025-05-09 19:43:13 UTC

The TIOBE index is crude, but it's exciting to see #Python continuing to shine: https://www.tiobe.com/tiobe-index/
Too bad about the simplistic and misleading summary: "[Python] is interpreted and thus prone to unexpected run-time errors."

2025-05-05 19:42:11 UTC

You can tell TOML is a backronym because the O definitely doesn't stand for Obvious: https://toml.io/en/v1.0.0#array-of-tables

2025-05-01 19:18:08 UTC

Another kind of bug revealed by including tests in your coverage:
with pytest.raises(ValueError):
process_data("bad data 1")
process_data("bad data 2") # never executed!
https://nedbatchelder.com/blog/202008/you_should_include_your_tests_in_coverage.html

2025-04-25 19:40:14 UTC

Q: What's the plural of regex?
A: regex{2,}
/ht Dathan Bennett

2025-04-01 19:30:56 UTC

Never let it be said that Python is slow to adopt new features: https://github.com/python/cpython/pull/131982
https://fosstodon.org/@ThePSF/114263169280378337

2025-03-18 12:38:47 UTC

If your test suite can run on #Python 3.14, and you use branch coverage measurement, please get Python 3.14.0a6 and coverage․py 7.7.0 and let me know how the speed compares to older versions! It will be faster!

2025-03-09 20:40:04 UTC

I could use some real-world testing of this if you are up for building the latest main branch of CPython:
https://hachyderm.io/@coveragepy/114134399532444539

2025-01-28 02:08:55 UTC

Python 1.0.0, released 31 years ago today:
https://groups.google.com/g/comp.lang.misc/c/_QUzdEGFwCo/m/KIFdu0-Dv7sJ
--> Tired of decyphering the Perl code you wrote last week?
--> Frustrated with Bourne shell syntax?
--> Spent too much time staring at core dumps lately?
Maybe you should try Python, the next generation object-oriented
scripting and prototyping language, with a *readable* syntax. Python
has been used by hundreds of happy users all over the world during the
past three years, and is now ready for prime time.

2024-12-17 15:38:51 UTC

Announcing the Partition Principle of #Python Pedagogy:
No matter what you are showing people or how unusual it is, if it uses str.partition() most of the comments will be, "I didn't know about str.partition()!"
https://docs.python.org/3/library/stdtypes.html#str.partition
BTW: also str.rpartition()...

2024-12-17 11:42:42 UTC

Some nice #pytest techniques here as @nprofile…6nq0 updates my "Testing some tidbits" post: https://pythontest.com/pytest/testing-tidbits-pytest/

2024-12-14 14:53:44 UTC

Is this the greatest song ever? Code Monkey by Jonathan Coulton.
https://www.youtube.com/watch?v=AEBld6I_AKs

2024-12-12 11:49:47 UTC

Is this #Python too compact? Perhaps, but there could be useful things to learn. Full explanation unpacked at https://nedbatchelder.com/blog/201802/a_python_gargoyle.html
https://media.hachyderm.io/media_attachments/files/113/639/698/234/078/742/original/34035f5794b3a1fc.png

2024-12-06 16:40:36 UTC

Splitting a string once in #Python: .split() has maxsplit=, but .partition() can be better:
https://media.hachyderm.io/media_attachments/files/113/606/867/963/003/024/original/e748b71dd1c5e745.png

2024-12-02 15:06:30 UTC

Got an email, "Thank you for coverage.py." Opening it, I saw a number of paragraphs. I immediately thought, "they're going to want something, or complain about something."
Nope! It was details of their challenges, and how coverage.py helped, especially the documentation. Ended with "Thanks again for this awesome Python contribution!"
If you like what someone has done, tell them!

2024-12-01 16:02:30 UTC

You can write short powerful #Python expressions using its many tools. Are there other ways to check if a string contains only "0" or "1"?
https://media.hachyderm.io/media_attachments/files/113/578/406/598/554/875/original/8247ff6c5526caa6.png

2024-11-26 18:34:09 UTC

Are you using #Python 3.11 yet? It's been out for two years! Maybe this will entice you: better error messages!
https://media.hachyderm.io/media_attachments/files/113/550/691/314/268/082/original/729d2e921abf3305.png

2024-11-24 19:14:37 UTC

Classes in #Python can define their own formatting mini-languages for f-strings by defining __format__. Full details: https://nedbatchelder.com/blog/202204/python_custom_formatting.html
https://media.hachyderm.io/media_attachments/files/113/539/525/865/117/128/original/0cbfeea20af6652d.png

2024-11-22 17:13:13 UTC

What if you want space around the word before centering? Is #Python letting me take this too far? Nested f-strings!?
https://hachyderm.io/@nedbat/113520644869408039
https://media.hachyderm.io/media_attachments/files/113/527/723/903/271/745/original/808048d2483e777f.png

2024-11-21 17:50:14 UTC

Also: you can also use variables (or expressions?!) for the formatting information! #Python is cool...
More details and explanation at https://fstring.help
https://hachyderm.io/@nedbat/113520644869408039
https://media.hachyderm.io/media_attachments/files/113/522/207/099/195/547/original/723d13928dfdbdfd.png

2024-11-21 11:12:54 UTC

String formatting in #Python lets you left-, right-, or center-justify a value. You can specify the fill character to use. The syntax is colon, fill-char, <^>, width:
https://media.hachyderm.io/media_attachments/files/113/520/644/737/322/977/original/2d510b0b29a8b449.png

2024-11-19 12:17:18 UTC

More explanation about this tidbit: https://nedbatchelder.com/blog/202411/loop_targets.html
https://hachyderm.io/@nedbat/113498200513086976

2024-11-17 12:05:00 UTC

For loops in #Python can assign to more than just plain names. Any assignment target is allowed:
https://media.hachyderm.io/media_attachments/files/113/498/200/375/008/299/original/6634d756fcab33bb.png

2024-11-02 11:41:53 UTC

People make project maintenance sound like such a big deal, it's not! Mostly it's just writing some yaml to make sure the other yaml is still properly yaml'ing the old yaml.... :(

2024-09-10 14:53:03 UTC

I just noticed this misplaced line that I've walked over hundreds of times. How is your morning going?
https://media.hachyderm.io/media_attachments/files/113/113/824/036/135/252/original/115f8e6db7d6d3b4.jpg

2024-09-09 23:48:45 UTC

We're starting work to refactor the #Python devguide into a broader and more inclusive Contribution Guide: https://discuss.python.org/t/refactoring-the-devguide-into-a-contribution-guide/63409

2024-08-16 00:08:32 UTC

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@npub1f6a…pnql I wrote something that does a little bit of this: https://github.com/nedbat/pydoctor

2024-08-12 17:29:16 UTC

NASA(!) is asking me for "country of origin" for coverage․py. Is there a useful explainer I can point them at explaining why this question makes no sense? Or do I just say USA because that's where I live?

2024-08-11 19:24:14 UTC

Hot #Python take: textwrap.dedent is great, but inspect.cleandoc is better (and it should be in textwrap, not inspect).
https://docs.python.org/3/library/inspect.html#inspect.cleandoc
(Actually not a hot take, it's carefully considered!)

2024-08-11 18:06:50 UTC

Advice for new parents: https://nedbatchelder.com/blog/202408/cherish_this_time.html

2024-07-21 21:07:57 UTC

Also: you don't need to have an opinion if you have no control over the outcome. Focus on things where your attention has an effect: donate, write letters, get out the vote.
https://botsin.space/@orcspiration/112825977790154105

2024-07-16 19:43:30 UTC

I am starting a new job next week at Anthropic: https://nedbatchelder.com/blog/202407/anthropic.html

2024-06-23 19:50:48 UTC

Since #Python's pathlib.Path lets you use `/` to join paths together, why not this to get absolute paths?
abs(Path.home() / "my_file")
https://discuss.python.org/t/add-floordiv-to-pathlib-path-for-strict-append/1077/6

2024-06-17 15:59:52 UTC

Is there an example out there of a freemium-like model for open source? Pay a little to get the latest cool stuff a year before the public. Everything is eventually free for everyone, but money gets you on the inside track. Crazy idea?

2024-06-14 13:22:22 UTC

Coming from an experienced perspective, the most surprising common question in the #Python Discord (https://discord.gg/python) is, "what's the difference between return and print?" or "why return when you can just print?"

2024-06-12 11:05:16 UTC

Is there a more 2024 changelog entry than this, from a *terminal emulator*?
> This release adds some safety valves to eliminate the risk of private information leaving the terminal via the AI endpoints.

2024-06-09 11:22:22 UTC

I guess the time has come. I think I have to finally figure out what #Python's sys.meta_path does...
https://docs.python.org/3/library/sys.html#sys.meta_path

2024-05-25 11:22:02 UTC

Small fix to watchgha: don't truncate lists at 30 items (oops!)
WatchGHA reports on GitHub Action progress in a terminal UI.
https://pypi.org/project/watchgha/
https://media.hachyderm.io/media_attachments/files/112/501/464/760/292/232/original/87e891cac29017ca.png

2024-05-24 21:32:31 UTC

The joy of trying to be on the cutting edge of #Python:
HTTPError: 400 Bad Request from https://upload.pypi.org/legacy/
'Programming Language :: Python :: 3.14' is not a valid classifier.

2024-05-22 23:19:57 UTC

It's impossible to sum up #PyConUS. But i wanted to note a few things, including yet another appearance of Sleepy Snake: https://nedbatchelder.com/blog/202405/echos_of_the_people_api_user_guide.html

2024-05-16 11:22:03 UTC

I'm headed to #PyConUS today, arriving in the middle of the opening reception (if all goes well). I'll be trying to clump together with other dinner-foragers...

2024-05-14 18:09:49 UTC

Yes, test freethreading Python!
I added this line to my GitHub Action step to show the environment:
python -c "import sys; print('GIL:', getattr(sys, '_is_gil_enabled', lambda: True)())"
https://mastodon.social/@hugovk/112440452061115479

2024-05-13 11:30:52 UTC

Remember that #Python dicts can have tuples as keys! Consider a dict with (x,y) keys instead of nested lists for a grid. It simplifies sparse grids, "resizes" are automatic, it doesn't matter where (0,0) is, and you can use negative positions:
https://media.hachyderm.io/media_attachments/files/112/433/551/760/419/210/original/995353a6b9000982.png
https://media.hachyderm.io/media_attachments/files/112/433/551/786/793/854/original/ccd9a84b47e396e8.png

2024-05-08 20:23:27 UTC

People in this thread are suggesting other terms besides "slop", but slop works really well because of the parallel to the existing meaning: food that used to be fit for human consumption, but now is just leftover pieces mixed and mashed indiscriminately so that it's used to feed pigs.
https://fedi.simonwillison.net/@simon/112406874796870923

2024-04-29 10:37:01 UTC

My test suite has just one dot on the last line. What would you do?
- Delete one test
- Change the width of the terminal
- Keep it as a visceral reminder of the uncomfortably chaotic nature of the universe
- Write more tests
https://media.hachyderm.io/media_attachments/files/112/354/057/656/071/860/original/0d7db30c8ad6ebc5.png

2024-04-22 10:29:31 UTC

A difficult thing when writing docs: wanting to use English words that have more specific meanings in Python. Like "Values should be in the set returned by all_possibilities()" when all_possibilities returns an iterable, not a set.

2024-04-21 18:02:25 UTC

Anyone remember what #PyCon talk it was where somehow the captioner got in a discussion with the speaker and typed "I'm in the room" into the captions?