fidzu : python

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29 Jun 2026 11:05pm GMT

For June 2026, we welcome Salim Nuru as our DSF member of the month! ⭐

Salim was a Djangonaut Space participant in the first session. He has been an organiser of the DjangoCon Africa conference. He is currently the chair of the DjangoCon US website. He a DSF member since October 2024. He is looking for new opportunities!

You can learn more about Salim by visiting Salim's blog and his GitHub Profile.

Let's spend some time getting to know Salim better!

Can you tell us a little about yourself (hobbies, education, etc)?

I'm Salim, I'm from Addis, Ababa Ethiopia. I'm a software engineer by day and a security researcher by night. And for fun, I like chess, video games, and books.

I already have an idea, but where does your nickname "theShinigami" come from?

I LOVE anime, and the very first anime I watched was Death Note. There's this character called Ryuk, who is a "shinigami," and when I created my GitHub account, it was a time when I was really into anime (which I still am). That's why it stuck as my GitHub username.

How did you start using Django?

I started using Django during my college years. I was doing freelance work and mostly using .NET and JavaScript, when I got a huge project that needed to be built with Django. I didn't want to pass up the opportunity. At that time, I had heard about Django but never gotten to use it, so I had a week to prepare and spent every minute of it learning Django. I liked how easy it was to learn.

What other frameworks do you know, and is there anything you would like to have in Django if you had magical powers?

From Python based frameworks, I use Flask, FastAPI, etc. And I would like Django to support REST APIs out of the box.

What projects are you working on now?

I have a couple of projects I'm working on currently, and the one I'm proud of and actively working on is a platform that scans an Android app and gives security suggestions. It also has an AI that can do a deep scan and suggest a proof of concept if any vulnerabilities are found in the app. This is my first project that involves AI and running my own local LLM for security.

Which Django libraries are your favorite (core or 3rd party)?

There are a lot of great libraries, but the Django Debug Toolbar has a special place in my heart. Also Django Rest Framework (DRF), which I use for most of the projects I work on.

What are the top three things in Django that you like?

Community, security by default, and finally the admin panel.

I know you have a lot of knowledge in cyber security. How do you find the security in Django? Have you ever thought about being part of the security team, by any chance?

I'm still learning, and in Django I like how it applies security by default, which is a good thing. For now, I'm replicating the CVEs found in Django, just trying to understand them and find my next CVE in Django 🤞, and hopefully it would be great to work with the Django security team 🙂

You have been an organizer of DjangoCon Africa, thank you for organizing it. Organizers always do a lot of work that people can't see. How did you start? What are the things that have surprised you or that you didn't expect as an organizer?

Organizing is a team effort. I like the saying "there is no "I" in DjangoCon US" 🙂

I attended my very first DjangoCon at the very first DjangoCon Africa, as a speaker, and I really enjoyed it. I liked how the community was really welcoming and friendly, and right there and then I decided that this was going to be my community and that I had to do my part.

So I joined the organizing team for the next DjangoCon Africa, and after organizing it, I was really surprised by how many people from the community joined the event, and how far they had come just to attend the conference.

You are now the chair of the DjangoCon US website that's amazing! What does it mean exactly? How has your experience been so far?

Well, if people want to know anything about the conference, they're going to be checking out the website, and as the chair, I should be able to make that experience great. As for my own experience, I think it's really great and a step up in role. I'm learning a lot, and I'm very happy that I'm able to do it.

You now have some experience in organizing big events. Do you have any recommendations for people who would potentially be interested in contributing to or organizing this type of event?

Don't wait to feel ready, because that feeling rarely comes. Take on a small role first, lean on the people around you, and keep everyone in the loop. So to anyone considering it, I'd say jump in, the experience is well worth it.

You have been part of the Djangonaut Space program as a djangonaut (participant), and you are now involved in the community in many ways. How do you reflect on your evolution since your participation in the program? Any advice for potential new contributors or people who would like to give it a try?

When I joined Djangonaut Space as a participant, I would say that was the highlight of my year, because I always wanted to contribute to open source, especially to Django and Python projects, but I always hesitated to do it. The program really helped me, from picking my first issue to creating the PR (a big shoutout to Fabian, lead maintainer of Django CMS) it was really amazing. And for any new contributors, if you're planning to join Djangonaut Space, it's not just going to help you with your open source contribution, you're going to be joining a community.

Do you remember your first contribution to Django and to open source?

My very first contribution was to a tool for binary instrumentation. I was doing some reverse engineering, but there was a bug that made it difficult, so I had to understand and fix the bug and then create a PR. I remember getting good feedback and having a good interaction via Discord, and the PR was finally merged 🙂. In Django, it was django CMS, and the issue I worked on was the missing X-Frame option from the Advanced form (#7981). It was a great first issue, and it taught me a lot.

Is there anything else you'd like to say?

I'd just like to thank the Django community for being so welcoming to newcomers, and I'm looking forward to making new contributions (especially in security) 🙂.

Thank you for doing the interview, Salim !

29 Jun 2026 7:59pm GMT

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The post Python eBook and Course Summer Sale appeared first on Mouse Vs Python.

29 Jun 2026 5:38pm GMT

Maintaining a mature, reasonably-popular Django open-source is boring. Here I explore using a LLM to automate away some of the boring work.

28 Jun 2026 3:00am GMT

I recently attended my first PG Data 2026 conference where keynote speaker Robert Haas delivered a talk that has stayed with me. His keynote focused on the people behind PostgreSQL, the growing challenges of sustaining open-source communities, and the urgent need to cultivate new contributors through mentorship and community engagement. While his remarks centered on PostgreSQL, they sparked broader reflections for me about the future of open source and communities like Django.

26 Jun 2026 7:00pm GMT

News

Django 6.1 beta 1 released

Django 6.1 beta 1 is now available, giving the community a chance to test upcoming features and improvements before the final release on August 5.

Djangonaut Space: Launching Contributors

Djangonaut Space shares the results from its first six mentorship sessions, showing how an 8-week cohort program helped launch 104 contributors from 40+ countries into long-term open source participation and leadership.

Django Software Foundation

How the Django Software Foundation Became a CNA

Learn how the Django Software Foundation became a CVE Numbering Authority, giving it the ability to assign CVE IDs directly and streamline Django's security advisory process.

Wagtail CMS News

Wagtail as Django admin on steroids

Think Wagtail is just a CMS? See why it can serve as a polished, modern replacement for Django's admin with a familiar API and powerful features that make client-facing backends shine.

Comparing open weight AI models and providers

Open weight AI models are closing the gap with proprietary LLMs, and this guide explains how to compare models and providers on performance, cost, energy use, and transparency.

Releases

Python 3.15.0 beta 3 is here!

Python 3.15 beta 3 is out with nearly 200 bug fixes plus major additions like lazy imports, frozendict, sentinel objects, a faster JIT, and UTF-8 as the default encoding.

Updates to Django

Today, "Updates to Django" is presented by Raffaella from Djangonaut Space! 🚀

Last week we had 24 pull requests merged into Django by 16 different contributors - including 2 first-time contributors! Congratulations to Margaret Fero and diaxoaine for having their first commits merged into Django - welcome on board!

• EmailMessage.message() now raises a ValueError if Bcc is included in the headers argument or extra_headers attribute. Use the bcc argument instead. #37152
• Calling QuerySet.aiterator() after prefetch_related() without providing a chunk_size is deprecated. It currently falls back to a chunk_size of 2000, but a ValueError will be raised in Django 7.1. #37143

Articles

Teach your linter your own rules

boa-restrictor is a Python/Django linter that now lets you register your own AST-based rule classes via pyproject.toml to enforce project-specific conventions. This is especially useful as a deterministic guardrail for keeping AI coding agents from repeating unwanted patterns.

Why I wrote PEP 832 -- virtual environment discovery

PEP 832 proposes a standard way for editors and AI tools to discover Python virtual environments, aiming to make project setup smoother regardless of your workflow tool.

Supporting Django's Next Chapter

Caktus Group has become a founding sponsor of the Django Software Foundation's new Executive Director position, investing in Django's long term sustainability and encouraging other companies to do the same.

Mitigated API authentication bypass for python.org download metadata

Python.org has disclosed and mitigated an authentication bypass that could have altered download metadata, with no evidence of exploitation after extensive audits and additional security hardening.

How I Architected Automatic Parking Detection in Django - Bluetooth Disconnects, Geofence Events, and a Strict State Machine

A deep dive into building a reliable Django parking detection system using Bluetooth events, geofencing, state machines, and optimistic locking to safely handle concurrency.

What I learned from two days of hanging out with AI experts

Five practical takeaways from an AI conference suggest the future belongs to model agnosticism, measurable ROI, and smaller open models instead of hype.

Videos

Learning Python in the Age of AI

In this short interview from PyCon US, Sheena O'Connell discusses one of the biggest questions facing developers today: how should people learn Python in the age of AI?

Paolo Melchiorre on AI-Assisted Development

Another PyCon US 2026 chat, this time with Paolo Melchiorre talking about Django, AI-assisted development, open-source maintainership, and how the Python community is adapting to AI.

Django Forum

Django 6.1 release - timeline and next steps

Notes and updates from Fellow Jacob Walls on the 6.1 release process.

Adding database backend methods to get hardcoded or nonexistent primary key values for tests

From Tim Graham, surfacing ticket #37175 "to see what our creative community can suggest."

Django Fellow Reports

Jacob Walls

Tended to a flurry of fixes before the non-release-blocker bugfix freeze for Django 6.1 in a few days. Also chipped away at some performance improvements for ASGI projects using sync middleware.

Natalia Bidart

Lots of preparation for the upcoming 6.1 βeta, with the goal of stabilizing recent changes and ensuring overall readiness 🚀. I also spent time digging into Django's async behavior, reviewing recent changes and following through on related optimizations and documentation updates 📒. I also looked more closely at packaging and reproducibility, especially around artifact builds, to improve our consistency in the release process 📦.

Django Job Board

Senior Python/Django Developer at Gryps

Founding ML/Data Scientist (Remote, UK) at MyDataValue

Projects

vintasoftware/django-ai-boost

A MCP server for Django applications, inspired by Laravel Boost.

Archmonger/ServeStatic

Production-grade Python static file server. Run as middleware or standalone.

26 Jun 2026 3:00pm GMT

As I have discussed in previous posts, "AIs" can make mistakes. In fact, they do make mistakes, and their mistake-making patterns are such that where and how they will make mistakes is both uncertain and constantly changing.

Thus, in any scenario where you want to attempt to make "productive" use of "AI", you must have a system in place for checking every result. Not checking some results; checking every result. If each result might have a consequence for you (and if it didn't have a consequence, why bother automating it?) and you cannot predict in advance which kinds of results will need verification, then verification is always required.

The verification often ends up being just as expensive as doing the work in the first place, which means that if you want your usage of "AI" to be personally profitable, you have to find someone else to externalize the cost of verification onto. This person becomes your adversary, and, if you are successful, your "AI's" victim.

The Ladder-Climber And Their Reverse-Centaur Rungs

One way that this constellation of facts can straightforwardly assemble themselves into a dystopian nightmare is the phenomenon, described by Cory Doctorow, of the reverse centaur. This is when your employer non-consensually turns you into the verification system. The "AI" does the fun part of initially performing the work, and then you do the boring part where you check if the robot is right and clean up its messes, even if everyone already knows that it would, in aggregate, be cheaper for you to do the work in the first place.

Reverse centaurs can be made from any automation, not only "AI" automation. I think that there is a reason that this term happens to have emerged in the "age of AI", though, and not with earlier automation technologies (even those which were considerably more viscerally horrific). That reason is: the wrongness of "AI" output is not merely a technical feature that must be compensated for, it is a generalized externality.

As I mentioned above, if you are responsible for the entirety of the work, both extruding the "AI" output and checking it, it's usually cheaper to have humans do the entirety of the work to begin with. When humans do the writing directly, we can check as we go, and thus verification doesn't need to be as comprehensive.

When "AI" coding advocates say "code review is the bottleneck", what they are observing is that the LLM is still rolling the dice for each PR, and a human is still necessary to verify that each of those rolls is a winner. But calling this process "code review" is a bit of a misnomer; it's not really "code review" in the traditional sense, it's human understanding.

Before the advent of "AI", the human understanding was implicit in the process of writing the code in the first place¹, and the code review was a way of diffusing and extending that understanding. Now that the code can be authored with no initial understanding taking place, that cost has not gone away, it has moved.

Human understanding was always the bottleneck.

However, this is taking a collaborative view of a software project, where satisfying the needs and solving the problems of your customers are the goals. We can see that "AI" is a bad tool to satisfy those goals, because all it's doing is converting the first half of the work, that of understanding the code as you write it, to understanding the agent's output as you read it.

What if, instead, we were to take the view that every software company is a Hobbesian nightmare, red in tooth and claw? In this view, the only goal of a software project is for the individual developers to make their promo cycles and get their bonuses. Given that there is only a certain amount of money to go around, this is a zero-sum game where each programmer wants to look more productive than their colleagues.

Pretty much every organization finds it easy to reward "productivity" as expressed by lines of code emitted, but the benefits of doing thorough and thoughtful design, analysis, and code review very difficult to reward. In this world, an LLM is an invaluable tool for the sociopathic ladder-climber, particularly if your legacy organization is still structuring their workflows as if the person prompting the bot is "writing" the code, and then they get to foist off the act of "reviewing" the code onto someone else.

Here, the prompter effectively externalizes the cost of the LLM's failures but internalizes any benefits. The prompter will vibe-code a big feature, so large that the assigned reviewer can't possibly comprehend it all effectively. When this happens, the reviewer will, eventually, be pressured to approve it, even if they can try to spot a few problems along the way. The reviewer has their own work to get back to, after all, the obligation to review the prompter's (read: the bot's) code is a drain on their time that they are not going to get rewarded for.

If this feature is a big success, the prompter gets a promotion. If it causes a big issue, well, the reviewer must not have been careful enough.

This is why LLMs are "good for coding", and also why their biggest promoters keep having outages.

The Generative Gish Galloper

Coding is the biggest "success story" of this type of adversarial communication, but it is by far not the only instance of such a thing. LLMs create a new form of leverage that can turn Brandolini's law from a linear advantage into an exponential one. If you are engaged in a political debate where you want to overwhelm the other side in nonsense, an LLM can generate bullshit faster than it is physically possible for a human being to type, let alone respond thoughtfully. There is an asymmetry to the utility of this weapon as well: only one side of the political spectrum wants to flood the zone and destroy trust in institutions and the concept of truth. There's a good reason that the fascists love it.

Straightforward Spam and Fraud

This is kind of obvious, but LLMs can generate lightly-customized, plausible-looking text much more quickly than any human being. This facilitates their use in fraud, spam, and scams. In a spamming or fraudulent interaction, once again, the costs are externalized onto the victim: the recipient of a spam message has to do all the work of "checking" the LLM's output. Spammers already expect very low hit rates from boilerplate, and if the LLM can increase those percentages from 1% to 5% the technology will pay for itself; they don't need anything like reliable accuracy.

Customer "Support"

If you have any kind of commercial relationship with a company, I probably don't even need to mention this: customer "support" bots are a misery. Everybody knows it at this point. But customer support is usually conceptualized by businesses as an adversarial interaction, because it is a cost center. They maintain internal metrics on time-to-resolution and try to optimize them. Implicitly, this creates a dynamic where the goal of the customer service agent's job is not to solve your problem, but to emit noise that will cause you to think your problem is resolved, or to give up, as fast as possible. Unsurprisingly, LLMs can emit this noise faster than humans can, getting those customers off the phone. But those customers will remember those interactions, and the story outside the TTR metrics is horrible.

Similarly to the situation in software development, LLMs can look very good on paper for customer support, but mostly what they are doing is illuminating the problems with the industry's existing metrics, by turning "winning the metrics battle against the customer" into a more obvious and immediate defeat for the company's long term reputation.

"Education"

In 2026 it is sadly a fact of life that students cheat all the time using "AI", and that this cheating is very successful, in that the teachers find it very hard to detect.

LLMs are great for cheating on schoolwork because the student is externalizing the work of the checking onto the teachers, who are often starting at a disadvantage to begin with, at least in the US.

My view is that this is happening because of a divergence in the way that students vs. teachers (or, more accurately, "the broader educational system") view grading.

When a student is asked to write an essay, the teachers see the effort as both intrinsically worthwhile for the student, as well as useful as a pedagogical tool to evaluate and react to the student's progress. The student, by contrast, sees a stumbling block designed to knock them off the path to success and into a permanent underclass. It is no wonder that the student sees "AI" as useful to their own goals and has no compunction about deploying it.

There is a bitter irony that the ability to understand the inherent value of actually writing the essay on their own is the sort of thing that students can really only learn by writing a bunch of essays. There's no way that I can think of which makes the benefit legible as long as a shortcut is available.

The net effect here is a downward spiral, where the already-wobbling educational system is sustaining an attack that it doesn't have the resources to recover from. The individual students' attacks against their teachers and their schools' grading systems might appear to momentarily succeed, but they will win the battle and lose the war.

Spamming "For Good"?

Usually when we talk about someone unilaterally choosing to enter into an adversarial relationship, that's an "attack" and for good reasons we have a negative impression of the attacker. However, I would be remiss if I did not point out that there are some cases where the relationship was already adversarial; just because you're the attacker doesn't mean that you are evil.

For example we might imagine use-cases like automatically filing appeals for prior authorizations against health insurance. It's relatively well-known at this point that the main way for-profit insurers maintain their margins is by denying claims right up to the line of the policies themselves being fraud, so using a spamming tool to fight them might be entirely justifiable² in that case.

Similarly, using an LLM could be justified in a fight against a company refusing to honor a warranty. One could imagine using an LLM to immediately generate replies and escalations.

However, even in imagined cases like these, the underlying problem is that the insurers and the vendors already have a tremendous amount of structural power, so it is more likely that they will have the advantage in deploying a communications weapon like an LLM, as well as enacting policies to simply ignore any LLM-based communication that you might submit. Worse, if these strategies were to become widespread, they might provide an excuse to reject any communications by feeding them into an unreliable "LLM detector" and issuing an automated "computer says no" even to hand-written correspondence.

It is also worth stressing that these cases are imagined, as compared to the very real coworker-abuse, spam, scam, fraud, and disinformation campaigns being waged in real life today.

Therefore, while legitimate uses might exist, it's hard to imagine that there's anywhere they would be genuinely valuable and sustainable. In the best case "AI" will provide a temporary advantage for underdogs that will provoke an arms race which the resource-advantaged adversaries will win in the long run, in the worst case the arms race itself will cement permanent structural change that will make things worse.

"Search" By Stealing

Most of the adversarial utility of "AI" is on the "write" side, since write-amplification is more obviously aggressive than reading. But the "read" side of LLMs - summarization and question-answering - can be a form of attack as well.

To begin with, the act of reading itself is currently enormously destructive, but that's arguably not a fundamental aspect of this technology. They could set reasonable rate-limits and respect things like robots.txt, as search engines have for decades now. They could also refrain from committing criminal levels of copyright infringement. But, today, using "AI" tools does suborn this sort of out-of-control crawling.

More insidiously, consider the scenario described in this YouTube video. The LTT Bros decided to try Linux again, and in the course of so doing, they had problems. When trying to solve these problems, they were faced with a choice: they could consult Reddit, or they could ask an LLM. Asking an LLM would "gaslight the heck out of" them, but they still found it preferable, because they would at least get an answer without getting yelled at.

Initially this sounds great. But it also means that you want to extract knowledge from a community, while mechanically eliding any values or norms that the community may want to impart as part of offering that knowledge. As someone who spent many years in a community tech support role, this is worrying. Many requests for support are people asking how to do things that will momentarily solve a superficial problem but create a long-term reliability problem or even an immediate security risk, that the question-asker doesn't want to hear about. Consider the question "I'm tired of entering my password so much, how do I make it so my laptop unlocks automatically". An obsequious chatbot will helpfully tell you how to do this without pushback.

But, this is also a sort of ethically murky area. The Linux community is somewhat famously, for many years now, a toxic cesspool of general hostility, misogyny, etc. It is certainly a good thing that people can get access to this knowledge without subjecting themselves to abuse. But it also means that the people with the power and the privilege to change the community for the better can just quietly withdraw, rather than fixing the problems. It also means that the positive elements of culture cannot be transmitted, and people will have no opportunity to learn about unknown unknowns.

In this case, the "adversarial" communication is with society. The thing that using an LLM for search lets you do is withdraw from society and avoid forming any personal connections. There are some personal connections which are painful and annoying, and so that can feel like a momentary balm. But the need to make connections in general is, like, the concept of society itself.

Who Am I Hurting?

LLMs are good at adversarial communication. They are so good at it, relative to their other benefits, that they will tend to make communications adversarial if you are not remaining vigilant about the possibility that it might do so. My request to you, dear reader, if you are going to use such tools, is to always ask yourself, "who might I be hurting, if I use an LLM for this?"

If you're using an "AI", who is its adversary? If you haven't given it one yet, who might the "AI" turn into an adversary? Who might you overwhelm with an asymmetric amount of output, or, if you're receiving information and not sending it, who are you taking that information from without consulting?

Figure out the answers to these questions and conduct yourself accordingly; the answer might be "yourself".

Acknowledgments

Thank you to my patrons who are supporting my writing on this blog. If you like what you've read here and you'd like to read more of it, or you'd like to support my various open-source endeavors, you can support my work as a sponsor!

23 Jun 2026 8:06pm GMT

Codecov's unreliability breaking CI on my open source projects has been a constant source of frustration for me for years. I have found a way to enforce coverage over a whole GitHub Actions build matrix that doesn't rely on third-party services.

09 Jun 2026 12:00am GMT

Let's say you're writing a Python library.

In this library, you have some collection of state that represents "options" or "configuration" for a bunch of operations. Such a set of options is a bundle of potentially ever-increasing complexity. Thus, you will want it to have an extremely minimal compatibility surface, with a very carefully chosen public interface, that is either small, or perhaps nothing at all. Such an object conveys state and might have some private behavior, but all you want consumers to be able to do is build it in very constrained, specific ways, and then pass it along as a parameter to your own APIs.

By way of example, imagine that you're wrapping a library that handles shipping physical packages.

There are a zillion ways to do it ship a package. There are different carriers who can ship it for you. There's air freight, and ground freight, and sea freight. There's overnight shipping. There's the option to require a signature. There's package tracking and certified mail. Suffice it to say, lots of stuff.

If you are starting out to implement such a library, you might need an object called something like ShippingOptions that encapsulates some of this. At the core of your library you might have a function like this:

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async def shipPackage(
        how: ShippingOptions,
        where: Address,
    ) -> ShippingStatus:
    ...

If you are starting out implementing such a library, you know that you're going to get the initial implementation of ShippingOptions wrong; or, at the very least, if not "wrong", then "incomplete". You should not want to commit to an expansive public API with a ton of different attributes until you really understand the problem domain pretty well.

Yet, ShippingOptions is absolutely vital to the rest of your library. You'll need to construct it and pass it to various methods like estimateShippingCost and shipPackage. So you're not going to want a ton of complexity and churn as you evolve it to be more complex.

Worse yet, this object has to hold a ton of state. It's got attributes, maybe even quite complex internal attributes that relate to different shipping services.

Right now, today, you need to add something so you can have "no rush", "standard" and "expedited" options. You can't just put off implementing that indefinitely until you can come up with the perfect shape. What to do?

The tool you want here is the opaque data type design pattern. C is lousy with such things (FILE, pthread_*_t, fd_set, etc). A typedef in a header file can easily achieve this.

But in Python, if you expose a dataclass - or any class, really - even if you keep all your fields private, the constructor is still, inherently, public. You can make it raise an exception or something, but your type checker still won't help your users; it'll still look like it's a normal class.

Luckily, Python typing provides a tool for this: typing.NewType.

Let's review our requirements:

1. We need a type that our client code can use in its type annotations; it needs to be public.
2. They need to be able to consruct it somehow, even if they shouldn't be able to see its attributes or its internal constructor arguments.
3. To express high-level things (like "ship fast") that should stay supported as we add more nuanced and complex configurations in the future (like "ship with the fastest possible option provided by the lowest-cost carrier that supports signature verification").

In order to solve these problems respectively, we will use:

1. a public NewType, which gives us our public name...
2. which wraps a private class with entirely private attributes, to give us an actual data structure, while not exposing the constructor,
3. a set of public constructor functions, which returns our NewType.

When we put that all together, it looks like this:

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from dataclasses import dataclass
from typing import Literal, NewType

@dataclass
class _RealShipOpts:
    _speed: Literal["fast", "normal", "slow"]

ShippingOptions = NewType("ShippingOptions", _RealShipOpts)

def shipFast() -> ShippingOptions:
    return ShippingOptions(_RealShipOpts("fast"))

def shipNormal() -> ShippingOptions:
    return ShippingOptions(_RealShipOpts("normal"))

def shipSlow() -> ShippingOptions:
    return ShippingOptions(_RealShipOpts("slow"))

As a snapshot in time, this is not all that interesting; we could have just exposed _RealShipOpts as a public class and saved ourselves some time. The fact that this exposes a constructor that takes a string is not a big deal for the present moment. For an initial quick and dirty implementation, we can just do checks like if options._speed == "fast" in our shipping and estimation code.

However, the main thing we are doing here is preserving our flexibility to evolve the related APIs into the future, so let's see how we might do that. For example, let's allow the shipping options to contain a concrete and specific carrier and freight method:

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from dataclasses import dataclass
from enum import Enum, auto
from typing import NewType

class Carrier(Enum):
    FedEx = auto()
    USPS = auto()
    DHL = auto()
    UPS = auto()

class Conveyance(Enum):
    air = auto()
    truck = auto()
    train = auto()

@dataclass
class _RealShipOpts:
    _carrier: Carrier
    _freight: Conveyance

ShippingOptions = NewType("ShippingOptions", _RealShipOpts)

def shipFast() -> ShippingOptions:
    return ShippingOptions(_RealShipOpts(Carrier.FedEx, Conveyance.air))

def shipNormal() -> ShippingOptions:
    return ShippingOptions(_RealShipOpts(Carrier.UPS, Conveyance.truck))

def shipSlow() -> ShippingOptions:
    return ShippingOptions(_RealShipOpts(Carrier.USPS, Conveyance.train))

def shippingDetailed(
    carrier: Carrier, conveyance: Conveyance
) -> ShippingOptions:
    return ShippingOptions(_RealShipOpts(carrier, conveyance))

As a NewType, our public ShippingOptions type doesn't have a constructor. Since _RealShipOpts is private, and all its attributes are private, we can completely remove the old versions.

Anything within our shipping library can still access the private variables on ShippingOptions; as a NewType, it's the same type as its base at runtime, so it presents minimal¹ overhead.

Clients outside our shipping library can still call all of our public constructors: shipFast, shipNormal, and shipSlow all still work with the same (as far as calling code knows) signature and behavior.

If you need to build and convey some state within your public API, while avoiding breakages associated with compatibility churn, hopefully this technique can help you do that!

Acknowledgments

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22 May 2026 12:33am GMT