Rodrigo Girão Serrão 🐍🚀

Python 3.15.0 was just released! To celebrate, I'm doing 15 days of Python 3.15. Each week day, I'll write about a new Python 3.15 feature. We'll cover lazy imports, the new built-ins, the DX improvements, some new stdlib niceties, and MUCH more. I'll collect my posts here 👇

I can't remember Python before this. Before Python underlined the part of the line that raised the error. Who remembers what Python version this was added on?

Python is getting quite colourful!

Rodrigo Girão Serrão 🐍🚀 reposted

Trey Hunner

@trey.io

Python 3.10 reached end of life a couple weeks ago. If you maintain a library and you're wondering what's in Python 3.11 that you can use, here's a cheat sheet. Upgrading to Python 3.14 because you like to stay one Python version behind at all times? This cheat sheet's for you too. #Python

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Explicit lazy imports bsky.app/profile/math...

Python startup times just got faster. In 3.15, you can use the keyword `lazy` to make a lazy import (`math` and `Path` below). Lazily imported modules are only loaded WHEN they're used, and IF they're used. Use them to defer loading of modules that may not be required.

New built-in `sentinel` bsky.app/profile/did:...

What do you do when you can't use `None` as the default? You can use `object()`... Or a singleton class... Or another workaround... And all these hacks had flaws. That's why Python 3.15 introduced the built-in `sentinel`. You can use it to create placeholder values 👇

There are many benefits to using `sentinel`. One of them is that typing sentinels is much cleaner than typing any of the alternatives. That's because sentinels can be used as their own type. Just like `None` can 👇

mathspp.comsentinel built-inLearn how to use the sentinel built-in from Python 3.15 for placeholder values.

If you want to learn more about how to create and use placeholder values in 3.15, read the article below: mathspp.com/blog/pydonts...

What's an example usage of a module-level `__getattr__` you've come across?

mathspp.comExplicit lazy importsLearn how to use lazy imports to speed up the startup time of your Python applications.

If you want to learn more about explicit lazy imports. See use case scenarios. Learn how to make them backwards compatible. Etc. Read this blog post: mathspp.com/blog/explici...

I'm doing 15 days of Python 3.15. Follow @mathspp.com for the whole journey. And check my profile for the free email series.

What's the consensus on `sentinel` vs `None`? Assume no backwards compatibility concerns. Do you still use `None` for pretty much all “nothing” usages and use `sentinel` only when `None` doesn't cut it? Or are you going to default to `sentinel` for placeholders?

Who had this ridiculous idea of doing 15 blog articles about Python 3.15 in 15 days while also running 5 workshops in 10 days? My weekly Monday newsletter is delayed and will only be coming out tomorrow 🤞

The syntax highlighter on my website isn't keeping up with Python 😮‍💨

uv self update; uvx whatsnewt

mathspp.com15 days of Python 3.15 🐍🚀Learn about the Python 3.15 🐍 features that matter 🚀

Btw, how cool is this logo by @riecatnor.bsky.social and @georgically.bsky.social? Each day, I'll write about a new feature of 3.15. I'll post a highlight here and I'll write a full blog post at mathspp.com/blog You can also receive the highlights directly in your email 👉 mathspp.com/python-315

Top 5 Python 3.15 new features: bsky.app/profile/math...

🏆 Top 5 Python 3.15 features to start using today: 1. Lazy imports 2. New built-in `frozendict` 3. New built-in `sentinel` 4. Unpacking inside comprehensions 5. New sampling profiler Tachyon What's your top Python 3.15 new feature?

mathspp.comThe 5 most exciting new features of Python 3.15This article explains the 5 best new features of Python 3.15 with clear examples and explanations.

To learn more about each of these features, you can see examples and explanations here: mathspp.com/blog/the-5-m...

mastodon.socialHugo van Kemenade (@hugovk@mastodon.social)Attached: 1 image Python 3.15.0 release day (second attempt)! ✅ Release date updated in What's New in Python 3.15 https://github.com/python/cpython/pull/159053 ✅ No release blockers https://github....

It's happening! And to celebrate (?) I'm spending the next 15 days writing about Python 3.15 In a couple of hours I'll be sharing what I think are some of the most exciting new features of 3.15. See you in a bit!

Hugo van Kemenade@hugovk.dev

Python 3.15.0 release day thread over on Mastodon: mastodon.social/@hugovk/1174... #Python #Python315 #release

Am I the only one compulsively hitting F5 in the Python downloads page waiting for Python 3.15?

mathspp.comWhy OOP existsLearn the fundamental principles behind OOP and how they connect to the syntax of Python.

27 Aug

Why does OOP exist? Why does it work the way it does? What's up with the magic in `self`? If you're new-ish to OOP I expect this article to fundamentally change the way you understand OOP. (For the better!) If it doesn't, I failed. You can read it here 👉 mathspp.com/blog/why-oop...

26 May

Python functions summarised in sentence: “Functions either return something or they blow up” — A student of mine

24 Apr

Your frontier of competence is expanded by LLMs based on your current knowledge.

mathspp.comuv skills for coding agentsThis article shares two skills you can add to your coding agents so they use uv workflows.

20 Apr

I'm trying to reach out to Charlie Marsh @crmarsh.com because of the upcoming EuroPython conference. Do I know anyone here who can help me get to him? Thanks 🙏

Rodrigo Girão Serrão 🐍🚀 reposted

Fredrik Mellström

@traal.se

9 Apr

These uv Python skills for coding agents look promising. From @mathspp.com mathspp.com/blog/uv-skills

ngrok.comQuantization from the ground up | ngrok blogA complete guide to what quantization is, how it works, and how it's used to compress large language models

8 Apr

If you’re at PyCon Lithuania 🇱🇹 #PyConLT, join me to learn about the paradox of itertools.tee in the Diamond room at 11am. See you there!

Rodrigo Girão Serrão 🐍🚀 reposted

Sam Rose

@samwho.dev

25 Mar

I spent 2 months learning about quantization and am extremely proud of the post I've written about it. I think these are some of the nicest visuals I've ever made, and I love how this compression technique invented in 1898 is being used on the bleeding edge in 2026. ngrok.com/blog/quantiz...

23 Mar

I forgot a semicolon and my site was down for ~4 hours without me even knowing. The joys of programming. 😂

23 Mar

What's your favourite vanilla Python feature? (Abuses of the Python syntax are valid answers.)

openai.comOpenAI to acquire AstralAccelerates Codex growth to power the next generation of Python developer tools

19 Mar

Astral just entered into an agreement with OpenAI to integrate their Codex team! openai.com/index/openai...

17 Mar

Too many arrows?

12 Mar

Python decorators blueprint: a step by step explanation of the full decorator anatomy. Steal this for when you're writing your own decorators.

I wrote 0 blog posts in February. Today I already wrote 2. Go figure. 🤷

Came up with 4 random ways to do this. 2, I recommend you use them (although 1 doesn't work!) The other 2 are really cool — they use fixed points and `itertools.groupby` — but they'll be overkill 99.9% of times.

How do you collapse runs of adjacent spaces in Python? That is, shorter runs of 2+ consecutive spaces so there's only 1 space there? I can't come up with a simple/straightforward way to do it with `str.join` and I'm surprised... What am I missing?

I meant “This is, shortEN runs of 2+ [...]”

Rodrigo Girão Serrão 🐍🚀 reposted

Anže

@anze3db.pecar.me

27 Feb

Hey all! It's almost time for the next Python Lisbon Meetup! 🐍 On Thursday, pyctrl will be talking about exceptions. We'll cover the origin of exceptions, their usage in OOP, how best to manage them, and more. It's going to be exceptional! 💎

23 Feb

How do you read `*args` in a function signature? PLEASE reply with how you'd read it, I'm trying to prove someone wrong 🤣 Reposts are appreciated :D

23 Feb

I read it as “star args”.

Rodrigo Girão Serrão 🐍🚀 reposted

Sam Rose

@samwho.dev

19 Feb

What do LLMs see? I wrote a lil' tool that extracts the attention matrices out of open models and creates this typing visual, with each token's opacity changing according to its average attention score as the prompt progresses. Dimmer words are considered less important to the model.

19 Feb

`itertools.compress` explained in a simple diagram. Useful when you need to filter an iterable of data based on a second iterable of flags or selectors.

18 Feb

How does this slide look?

12 Feb

FINALLY had technical issues while delivering a remote talk. Today I got all of it! First, my computer froze and I couldn't even share my screen. Then, at some point my internet connection went POOF and I dropped off the call... 🤦 Hopefully now I'm good again for a dozen more talks.

meetup.comPython Users Berlin (PUB): The paradox of itertools.tee, Thu, Feb 12, 2026, 7:00 PM | Meetup📆 Agenda * 19:00 Welcome to the PUB (Python Users Berlin) – setting up * 19:15 Main talk * 20:00 Lightning talks * 20:30 Social gathering 🎙 Main talk by [Rodrigo Girão

12 Feb

Catch you there?

Veit Schiele@veit-schiele.de

Final preparations for the Python Users Berlin (@python.berlin) meeting tonight. I’m looking forward to meeting all the Pythonistas in Berlin and Rodrigo’s (@mathspp.com) talk on itertools.tee: www.meetup.com/python-users... #Python #Berlin

Rodrigo Girão Serrão 🐍🚀 reposted

Savannah Ostrowski

@savannah.dev

11 Feb

Stoked to share that the Steering Council has accepted PEP 814. frozendict is coming to Python 3.15! discuss.python.org/t/pep-814-ad...

discuss.python.orgPEP 814: Add frozendict built-in typeAfter careful deliberation, the Python Steering Council is pleased to accept PEP 814 – Add frozendict built-in type. The absence of an immutable dict counterpart has been a long-standing gap in Pytho...

Rodrigo Girão Serrão 🐍🚀 reposted

Python Software Foundation

@python.org

10 Feb

Introducing the PSF Community Partner Program! The PSF is very excited to announce this new in-kind offering that expands how we support Python community events and initiatives around the world, now and alongside future community support programs 💝🐍

pyfound.blogspot.comIntroducing the PSF Community Partner ProgramThe Python Software Foundation (PSF) is excited to announce the introduction of the PSF Community Partner Program. This new program is designed as an “in-kind” way for us to support Python events and initiatives with non-financial assistance through the use of the PSF logo and name, as well as promotional support via sharing qualified posts on PSF official social media accounts. The PSF looks forward to supporting Python community events and initiatives through this new program!The introduction of the PSF Community Partner Program grew out of our desire to find alternative ways to support the community during the pause of our Grants Program (read more about the resulting process below). Even so, we intend to continue offering this in-kind support program after the Grants Program reopens. Our big picture hope is that, over the long term, some community events and initiatives will continue to partner with the PSF while being financially dependent on sponsors and individual donors alone. The PSF is also working on the future of our Grants Program, including when and how we can reopen it in a way that ensures the program’s long-term sustainability while balancing the needs of the Python community. In light of the truly staggering outpouring of support from our community during the 2025 year-end fundraiser, we are now in a stronger position to reopen the Grants Program and are eager to give back in a thoughtful and sustainable way. More updates to come!As with the rollout of any new program, we anticipate small adjustments will need to be made for processes to flow smoothly and to ensure the program serves the Python community well. The PSF welcomes your comments, feedback, and suggestions regarding the new Community Partner Program on the corresponding Discuss thread. We also invite you to join our upcoming PSF Board or Grants Program Office Hour sessions to talk with the PSF Board and Staff synchronously. If you wish to send your feedback privately, please email grants@python.org.