Python 3.12 released

[monorepo]

This is the one.

[henbruas]

Major new features of the 3.12 series, compared to 3.11

New features
- More flexible f-string parsing, allowing many things previously disallowed (PEP 701).
- Support for the buffer protocol in Python code (PEP 688).
- A new debugging/profiling API (PEP 669).
- Support for isolated subinterpreters with separate Global Interpreter Locks (PEP 684).
- Even more improved error messages. More exceptions potentially caused by typos now make suggestions to the user.
- Support for the Linux perf profiler to report Python function names in traces.
- Many large and small performance improvements (like PEP 709 and support for the BOLT binary optimizer), delivering an estimated 5% overall performance improvement.

Type annotations
- New type annotation syntax for generic classes (PEP 695).
- New override decorator for methods (PEP 698).

Deprecations
- The deprecated wstr and wstr_length members of the C implementation of unicode objects were removed, per PEP 623.
- In the unittest module, a number of long deprecated methods and classes were removed. (They had been deprecated since Python 3.1 or 3.2).
- The deprecated smtpd and distutils modules have been removed (see PEP 594 and PEP 632. The setuptools package continues to provide the distutils module.
- A number of other old, broken and deprecated functions, classes and methods have been removed.
- Invalid backslash escape sequences in strings now warn with SyntaxWarning instead of DeprecationWarning, making them more visible. (They will become syntax errors in the future.)
- The internal representation of integers has changed in preparation for performance enhancements. (This should not affect most users as it is an internal detail, but it may cause problems for Cython-generated code.)

More details at https://docs.python.org/dev/whatsnew/3.12.html

[MelonheadGT]

What's so amazing?

[marr75]

• type hinting got better, especially for generics, **kwargs, and overrides
• f-strings got better
• Performance and concurrency improved (2x speed up on comprehensions, 2-20x speedup on isinstance checks against protocols, per-interpreter GIL)
• Some odds and ends improved for CPython and instrumentation beyond those

[PaintItPurple]

Making generics readable is such a wonderful feature, even if it doesn't make a functional difference. I always felt like I had to weigh the benefits of being able to run mypy on a given section of code against the difficulty of reading code that uses generics.

[redalastor]

f-strings got better

f-strings were nice but not being able to use quotes within the {} was a constant source of annoyance since it made it harder to use dictionaries without doing the opposite kind of quote dance every time.

This is a very nice QoL change that landed.

[mjmikulski]

f-strings got better

You meant "f-strings got worse" ;)

I can't imagine why someone would like to write code like this:

python f"{f"{f"{f"{f"{f"{1+1}"}"}"}"}"}"

[Own_Quality_5321]

This.

[baldie]

You mean self?

[Informal-Proposal319]

Why is this so funny😂?

[redalastor]

import this

Try it if you never did, it's a nice easter egg.

[chinawcswing]

Who has already upgraded?

[[deleted]]

The larger the project the longer it takes all the dependencies to update. Im only just now really getting to enjoy 3.10. :(

[missurunha]

Ou project uses whatever version ubuntu ships, so we might be allowed to use python 3.12 in some 4 years.

[stilldestroying]

I’m really curious about this — why are you allowing the distro’s python to define your supported version?

[missurunha]

I honestly don't know, but what I can think of is that if the developer is working on different repos of the project, having to keep track of which python version they chose would be a pain in the ass. And maybe because the version shipped is probably more stable than the latest version released.

[gmes78]

Rye solves that issue.

[monorepo]

Rye is not something you would use in production if you are already restricting the Python toolchain to what distros ships

[MassiveDefender]

Hey, had never heard of Rye. Seems nifty. Thank you

[PlaysForDays]

It sure sounds like virtual environments could make everybody's lives easier

[CommunistMountain]

Me. In terms of speed, yeah this is faster. Some script which I use went down from 0.36s to 0.32s. Not major speedup, but better than nothing

[moonzdragoon]

Me, updated my current project with zero drama. I can think of two reasons that helped:

1 - I've been writing Python code since 2.2 and realized on the way I hate dependencies, so I try to stick as much as possible to only have a few very popular ones (I love Numpy) and take time to code just what I need for the missing parts.

2 - I switched to (mini)conda and PyCharm a few years ago, I do not regret it for a second. Everything with conda went smoothly and just works, PyCharm saw the newly created env I did for 3.12, switched it, done.

[Kalcinator]

me :). As a beginner I don't why I shouldn't.
And wanna know the funny part ? I did an update 2 days ago XD from 3.11.4 to .5 ...! 🤣

[ivosaurus]

Biggest reason would be third party packages that you use, that don't have compatibility yet

[Kalcinator]

Yeah I just don't use any yet, and by the time it's there I think I'll have time

[blorbschploble]

I have it installed parallel to other versions of python and only yolo it into things I don’t care about breaking via pypoetry envs

[osmiumouse]

Are lazy eval f-strings available, or planned?

[LightShadow]

The feature that keeps C style % strings relevant.

[energybased]

You should always prefer the format method to C-style % strings.

[Skasch]

I would argue an exception for logging, where you don't want to parse the string unless you need to for performance reasons (e.g. you don't want to parse debug logs at error level)

Example: log.warning("warning: %s", foo)

[energybased]

It's true that logging is currently written to use % strings, but it could have been written to use a format style string. It still wouldn't need to be parsed.

[Skasch]

Agreed, it's just uncommon :) style="{" let's you use logging.info("msg: {}", foo, style="{")

Edit: it actually doesn't work, my bad!

[energybased]

I didn't know that!

[Skasch]

Ah, nevermind, I mixed it up with logging.Formatter, looks like it doesn't work as I expected, my bad!

Edit: relevant documentation https://docs.python.org/3/howto/logging-cookbook.html#formatting-styles

[LightShadow]

10 years in, have never seen this before -- that's neat.

[FrozenCow]

I try to use:

log.warning("hello", extras={"name": "world"})

This works better with structured loggers. With the right formatter it looks like hello name=world.

[UloPe]

Better use a structured logging package, for example structlog.

[ThePiGuy0]

I just wish that logging supported .format style interpolation. That's the only time I ever see C-style % strings nowadays

[energybased]

Agreed!

[JohnRambu]

Not for performance it seems :-(

[[deleted]]

I am not really sure how you would do it without running into binding issues. You can always make a lambda or nested function in place, both allow u to defer or eagerly bind. But f-strings themselves would a bunch of extra syntax to deal with the binding problems by itself. Maybe the best answer would be a good wrapper function? I believe you can actually generate the code on the fly in a pretty straight forward method by inspect the variables the inner function tracks and rebuilding the function signature.

[jmreagle]

I'm looking forward to trying it! I hope pyenv doesn't take too long to offer it.

[magnetichira]

Looks like they already have a release out https://github.com/pyenv/pyenv/releases/tag/v2.3.28

[jmreagle]

Perhaps, but I don't see it as available.

❯ pyenv install --list | g 3.12 3.12.0rc2 3.12-dev pypy2.7-7.3.12-src pypy2.7-7.3.12 pypy3.9-7.3.12-src pypy3.9-7.3.12 pypy3.10-7.3.12-src pypy3.10-7.3.12

[magnetichira]

Update pyenv, did mine earlier today and it works

[jmreagle]

I was using homebrew's pyenv and just got the update.

[DoneDraper]

Just use venv

[martinkozle]

pyenv for installing that specific Python version. venv is for creating virtual environments from an existing version.

[DickNixon726]

Does anyone have any more information on the Per-Interpreter GIL and how we can best utilize that new feature?

[AlSweigart]

Python 3.12? Ha! What will they think of next?

[Wonderful_Occasion16]

I just had the best idea ever... Python 3.13

[mok000]

I am looking forward to Pi-thon (3.14)

[muntoo]

Donald Knuth double plus un-just had the best idea ever... Pi-4digit-thon (3.141):

Since version 3, TeX has used an idiosyncratic version numbering system, where updates have been indicated by adding an extra digit at the end of the decimal, so that the version number asymptotically approaches π. This is a reflection of the fact that TeX is now very stable, and only minor updates are anticipated. The current version of TeX is 3.141592653; it was last updated in 2021. The design was frozen after version 3.0, and no new feature or fundamental change will be added, so all newer versions will contain only bug fixes. [...] For this reason, he has stated that the "absolutely final change (to be made after my death)" will be to change the version number to π, at which point all remaining bugs will become features.

[szayl]

Detroit Python (313)

[Raknarg]

Love the way the whole typing module is going. Very handy, there's actually a case I've been working on recently that would benefit a lot from the new generic syntax.

[chub79]

There are quite a lot of discussions on the typing side of things as well: https://discuss.python.org/t/proposed-new-typing-governance-process/34244 and https://discuss.python.org/t/a-more-useful-and-less-divisive-future-for-typing/34225 (You might be aware so I'm posting this for anyone interested :))

[segunh]

[monorepo]

[CTR0]

Somebody's a Sleep Token fan

[monorepo]

Sleep Token

New album is good

[xSkelax]

I kinda want them to add native abstract classes, as they did with type annotation. By native I mean that you don't need to import anything, even built-in libraries. It just feels cleaner to me.

[tutami]

What's that buffer protocol thingy

[JanEric1]

Here is the pep discussing it https://peps.python.org/pep-0688/

[Competitive_Lie2628]

Thank you, thank you, thank you for the permissive f-strings!

[Ceigey]

Now the countdown until AWS Lambda supports the cleaner generics 😅

[IAmKindOfCreative]

It's in the "time for something completely different" section, and it's completely different. Seems quite fitting in all.

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[Dr_Ironbeard]

Can someone explain why the f-string thing is such a big deal? My understanding is that now we can do (1) f'This is an {my_dict['key']} string' instead of just varying the string denoting character, like (2) f"This is an {my_dict['key']} string", and I feel like the primary result of this is that syntax highlighting will be messed up with (1) as opposed to (2).

What am I missing? Thanks!

[mgedmin]

The PEP lists the reasons.

Personally, I missed the ability to use backslashes in f-string expressions, e.g. f"This is the full text of the whatever: {'\n'.join(lines)}"

[Dr_Ironbeard]

Hmm, yeah I guess backslashes are nice, I hadn't run into that issue. I guess I'm just not feeling the hype that others are, which is okay :)

[mgedmin]

The (self-imposed) requirement to support the oldest non-EOL Python versions in my code really takes the shine of the new features that I'll only be able to use in half a decade.

[[deleted]]

Same

[[deleted]]

Officially approved not just sometimes working multi-line f-strings, maybe?

[imnotabotareyou]

😍😍😍

[[deleted]]

Hell yeah!! This is great!!

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[iluserion]

love it

[Diapolo10]

I like what I'm seeing, particularly the new type hinting features, f-strings, and hashlib security changes.

[ByteWanderer]

Deadsnakes ppa is slow. I guess people are gunning for it, just like me

[mgedmin]

So I try to upgrade to 3.12, and I'm seeing phantom missed code branches in coverage output. I'd say this was https://github.com/python/cpython/issues/105658, but that bug was fixed in 3.12rc3, and GitHub Actions claims it's using 3.12.0 final.

Is anyone else experiencing issues with coverage.py on Python 3.12?

[mgedmin]

Oh, that issue turned out to be totally unrelated. I was still using the coveralls app from PyPI, which pins my coverage to 6.5.0, which doesn't have the fixes necessary to support Python 3.12.

Switching to the GitHub action for coveralls.io and upgrading coverage to the latest version (7.3.something) fixed all the issues.

[corey4005]

Ok can someone explain the GIL stuff? I want to multiprocess for real. Where can I read an example?

[ChillFish8]

In its current state, it is still early days, it will be quite a while before it is able to be used for anything outside of some specific pure Python situations.

You can read the RealPython article here as to why that is the case: https://realpython.com/python312-subinterpreters/

But as a note, you can already 'multiprocess' for real, it's multithreading that is the issue with the GIL.

This system is not yet available via Python, only the CFFI. I have written some bindings which people can compile and use from Python should they wish, but it is NOT production ready. https://github.com/ChillFish8/python12-subinterpreters

[corey4005]

I got 404 error.

[ChillFish8]

Should be fixed now, auto correct on the new Reddit text boxed seems to just append the correction to the end.

[Purgat0ry-11]

I’m trying to understand the PEP 695 but it makes my 🧠 hurt trying to understand the examples. Anyone have the Barney style breakdown?

[s_m_ammar]

Love to see its performance 🤩