iiinova — where your digital self keeps evolving

Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 27/08/2026

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...

mathspp.com

Why OOP exists

Learn the fundamental principles behind OOP and how they connect to the syntax of Python.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 26/05/2026

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

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 24/04/2026

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

A diagram showing how LLMs are more useful if you know more a priori. Two circles of different sizes represent your current knowledge and the LLM extends either circle by the same amount, so if your initial circle is larger than your ending circle is also larger.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 20/04/2026

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 🙏

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Reposted by Rodrigo Girão Serrão 🐍🚀

Fredrik Mellström @traal.se · 09/04/2026

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

mathspp.com

uv skills for coding agents

This article shares two skills you can add to your coding agents so they use uv workflows.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 08/04/2026

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!

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Reposted by Rodrigo Girão Serrão 🐍🚀

Sam Rose @samwho.dev · 25/03/2026

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...

ngrok.com

Quantization from the ground up | ngrok blog

A complete guide to what quantization is, how it works, and how it's used to compress large language models

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 23/03/2026

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

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 23/03/2026

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

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 12/03/2026

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

Diagram showing the full decorator anatomy and the 9 parts that make up a general decorator.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 02/03/2026

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

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 02/03/2026

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.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 02/03/2026

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?

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Reposted by Rodrigo Girão Serrão 🐍🚀

Anže @anze3db.pecar.me · 27/02/2026

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! 💎

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 23/02/2026

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

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Reposted by Rodrigo Girão Serrão 🐍🚀

Sam Rose @samwho.dev · 19/02/2026

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.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 19/02/2026

`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.

Diagram showing how `itertools.compress` works, taking an iterable with data and an iterable with selectors and making a selection based on the Truthy/Falsy value of the selectors.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 12/02/2026

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.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 09/02/2026

This list is missing the soft keywords. How many are there, and what are they?

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 09/02/2026

I've written this Python function so many times I should no longer be confused by it... But I never know if it's def clamp(v): return min(max(v, low), high) or def clamp(v): return min(max(v, high), low) Always need to stop and think about it for a minute.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 03/02/2026

If they had used the built-in `range` this wouldn’t happen.

Photo of a set of buttons inside an elevator. From the bottom up, the numbers go 2, 0, 4, 5, 6, …

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 02/02/2026

It's pretty cool how much you can get done in Python with so little code if you leverage the standard library.

Python code snippet with the following code:

from collections import deque
from itertools import islice, tee

def nwise(iterable, n):
iterators = tee(iterable, n)
for offset, it in enumerate(iterators):
deque(islice(it, offset), maxlen=0)
yield from zip(*iterators)

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 30/01/2026

One of my students today made this mistake. If you have a project and want to test it, your tests will import your project. So, you need to install pytest as a dependency INSIDE your project. If you install it globally, when you run it, it can't see your own project.

Diagram showing how using uv to install pytest globally will isolate it from everything else, as it should. But if you're testing a package, you want to have pytest as a dependency of that package since it'll be able to find your own package code.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 30/01/2026

Dump JSON and make it Human-readable.

Diagram showing how using the parameters `indent` and `sort_keys` can make the output of dumping JSON much better in Python.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 29/01/2026

Parse JSON from a string with a single function call. Don't use this if you have JSON in a file. Use `load` for that. This is for when the data comes in a payload, for example.

Simple diagram showing how to use `json.loads` to parse a native Python object from a JSON string.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 28/01/2026

When writing CLIs and scripts for the terminal, use `sys.exit` to set the exit code of your program. ✅ An exit code of 0 means success; your program terminated without any issues. ❌ Any other integer exit code means “error”.

Diagram showing how to use `sys.exit` to set the exit code of a program and how to use the command `echo $?` to check the exit code of the last command in the terminal.

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Reposted by Rodrigo Girão Serrão 🐍🚀

EuroPython 2026, Kraków @europython.eu · 27/01/2026

“Nothing beats the smiles and thank you’s you get when the conference is over. Plus, it is an amazing feeling to be part of something bigger than yourself.” Check out the interview with @mathspp.com, Programme Team for EuroPython 2025 blog.europython.eu/humans-of-ep... #europython #conference

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 27/01/2026

Day 2 of my intermediate Python course: I didn't forget to start the recording. That's a great start to the day :D

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 27/01/2026

Before being added in Python 3.10, itertools.pairwise was commonly implemented in terms of itertools.tee. Isn't this elegant?

Diagram showing how to implement pairwise in terms of tee.

Code:
def my_pairwise(it):
it1, it2 = tee(it, 2)
next(it2)
yield from zip(it1, it2)

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 26/01/2026

`typing.reveal_type` explained: Runtime vs static type checking time.

The module `typing` provides a debugging aid, the function `reveal_type`.
When a static type checker encounters it, the static type checker emits a note with the _inferred_ type of the expression passed into `reveal_type`:

```py
def s() -> str:
return 3

reveal_type(s())
# Revealed type is "builtins.str"
```

The function `reveal_type` doesn't even need to be imported and the static type checker infers that `s()` is a string because of the return type `-> str`.
(The static type checker also complains about the fact that we're returning an integer from inside `s` while the function should return a string, but you'll see why I'm doing that in a second.)

At runtime, the function `reveal_type` prints the runtime type of the argument to `sys.stderr` and returns the argument unchanged:

```py
from typing import reveal_type

def s() -> str:
return 3

reveal_type(s())
# Runtime type is 'int'
```

At runtime, the type of `s()` is `int` because the function `s` returns the integer 3.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 25/01/2026

Python typing pop quiz. Take a look at the function `choice` shown below. Note how it's being called as `choice(3, "hey!")`. Will this type check or not? If it does, what's the revealed type? The right answer might surprise you! It surprised me. 🤷

Code listing with the following Python code:

from typing import reveal_type
import random

def choice[T](left: T, right: T) -> T:
if random.random() < 0.5:
return left
else:
return right

reveal_type(choice(3, "hey!"))

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 24/01/2026

This is how you learn to write really good code. In Python, and in any other programming language 👇

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 23/01/2026

Has anyone here, in the data science world, successfully moved from using conda/miniconda/... to using uv?

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 23/01/2026

Python has a flexible mechanism built into `pathlib` to look for files with filenames that follow a given pattern. You can use `[...-...]` to represent character ranges and `*` to match arbitrary text. But note that `glob` does NOT support regex syntax! This is just similar.

Diagram showing how character ranges and the asterisk can be used in `pathlib.Path.glob` to match multiple filenames that follow the same pattern.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 21/01/2026

These two typing features look similar... But they're very different. Here's how to use NewType and TypeAlias in Python 👇

Diagram with code snippets showing how to use TypeAlias and NewType. The content of the post walks through the diagram.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 21/01/2026

In hindsight, if you're seeing this on your phone, the QR code isn't very helpful... Just go to mathspp . com / drops 🤣

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 21/01/2026

Just finished scheduling 3 tips for today, tomorrow and Friday. If you want to get smarter about Python in just 3 min/day, follow the QR code to sign-up.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 20/01/2026

Convert data to a JSON string without writing to a file: Just use `json.dumps`! (The final S stands for String!) ```py import json data = {"k1": True, "k2": [73, 42, 10]} s = json.dumps(data) print(type(s), s) # <class 'str'> {"k1": true, "k2": [73, 42, 10]} ```

Diagram showing how to use `json.dumps` to convert data into a JSON string.

Code snippet:

```py
import json

data = {"key1": True, "key2": [73, 42, 10]}

dumped = json.dumps(data)
print(type(dumped), dumped)
# str {"key1": true, "key2": [73, 42, 10]}
```

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 19/01/2026

Let me teach you to break a Python law. Iterators can only be traversed once: ```py squares = (x ** 2 for x in range(3)) for sq in squares: print(sq, end=", ") # 0, 1, 4, for sq in squares: print(sq, end=", ") # <no output> ``` The second loop produces no output!

Diagram showing how to use `itertools.tee` to split an iterator. The code snippets of the diagram are the ones in the post.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 18/01/2026

`itertools.pairwise` takes an iterable and produces overlapping pairs of consecutive elements: ```py from itertools import pairwise queue = ["John", "Joe", "Ana"] for f, b in pairwise(queue): print(f"{f}'s ahead of {b}.") # John's ahead of Joe. # Joe's ahead of Ana. ```

Diagram showing how `itertools.pairwise` works.

Code snippet:

```py
from itertools import pairwise

queue = ["Harry", "Hermione", "Ron"]

for front, back in pairwise(queue):
print(f"{front} is directly in front of {back}.")
```

Output:

```text
Harry is directly in front of Hermione.
Hermione is directly in front of Ron.
```

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 17/01/2026

This uv cheatsheet lists 40+ of the most and useful uv commands. It groups the commands into 9 sections that correspond to major features/capabilities that uv has. The cheatsheet is free to download and comes in light mode, dark mode, and high-contrast mode. mathspp.gumroad.com/l/cheatsheet...

uv cheatsheet with 40+ commands and variations split into 9 categories.

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 16/01/2026

A regex match has the method `groups`. This method returns a tuple with all of the groups that the pattern contained. Here's an example 👇

Diagram showing how to use `re.Match.groups` with a default value. The code snippets in the diagram match the ones shared in the post(s).

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Rodrigo Girão Serrão 🐍🚀 @mathspp.com · 15/01/2026

If your code type checks and you don't have `Any` or `# type: ignore` then you won't get type errors at runtime. Right? Wrong... ```py x: object = [] hash(x) ``` This code type checks but raises a `TypeError` at runtime... What's going on here?

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