Python interview questions: what each one actually predicts on the job (2026)
Canonical: this is a cross-post. The original lives at https://four-leaf.ai/blog/python-interview-questions You can find a hundred Python interview qu…
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Stop Shipping ML Models With Bare Floats: A Deep Dive Into Statistically Rigorous Model Evaluation
Stop Shipping ML Models With Bare Floats Every week, somewhere, a team makes a deployment decision that looks like this: Model A: AUROC = 0.847 Model …
Power analysis for LLM evals: how big does your eval set need to be to catch a 5% regression?
TL;DR: Most eval sets are sized by "what we had lying around", not by what they can actually detect. If your eval set is 50 traces and you are trying …
From Variant CSV to Review-Ready Report: A Python Workflow With Docker and GitHub Actions
Variant prioritisation often starts with a table. But a table alone does not answer the most important question: Which variants deserve closer review,…
Can AI Reason From Marker Genes? Building a Single-Cell Benchmark From PBMC3k
Most single-cell RNA-seq examples end with this pattern: load data preprocess cluster cells generate UMAP rank marker genes assign cell labels That wo…
Your UMAP Looks Great. But Can You Prove the Annotation Is Correct?
How I built a production scanpy pipeline that does not just annotate single-cell data -- it measures how accurately it did so, where it fails, and why…
Python for Machine Learning: The Complete Roadmap Nobody Told You About
When I first started exploring Machine Learning, I made the same mistake most beginners do — I jumped straight into neural networks and model training…
How to Build a LinkedIn Profile Scraper: The Honest Technical Guide
If you have ever tried to build a LinkedIn profile scraper , you have probably discovered that the obvious path — "just call the API" — is a dead end.…
Why your synthetic fintech data fails code review (and how mixture models fix it)
Every fintech developer has done this: you need test data, you reach for Faker, you generate ten thousand transactions, and your demo works. Then a da…
Building GeoPrizm: Turning Global News Events into a Bilateral Relations Index
I recently built GeoPrizm , a free and open-source dashboard for tracking bilateral relations through global news event signals. The idea is simple: i…
How to Become a Data Scientist in 2026
How I got here On principle, you will never catch me parading myself as a some sort of expert data scientist. Technically, that's what I do in my day …
The Journey Begins: Week 1 as an Aspiring Data Professional.
Introduction Ladies and gentlemen, I believe in this era of social media, we have all come across content that encourages us to 'Awaken the beast wit…
I Built a Fraud Detection System That Catches 99.76% of Fraud — Here's Everything I Learned
There is a number that haunts every fraud detection engineer: 0.13% . That is the fraud rate in the PaySim dataset — 8,213 fraudulent transactions bur…
Excel For Data Analytics
Introduction Excel is a spreadsheet software that allows you to collect, organize, analyze, calculate, and visualize data efficiently. In the first we…
I built a data-contract validator in pure Python (no pandas, no PyYAML) and it caught a 30% revenue ghost
A few months ago I spent the better part of a day chasing a bug that turned out not to be a bug at all. A downstream dashboard showed revenue had jump…
Power BI Visual Monitoring: Automatically Detecting Broken Visuals in Power BI Reports
Key Use Cases Power BI Visual Monitoring can be used for: power bi visual monitoring power bi report visual monitoring visual regression testing for P…
Training a Twitch chat toxicity classifier on real VOD data at scale
Quick answer: Twitch has no public API for VOD chat replay. To build a Twitch toxicity classifier dataset you walk the internal VideoCommentsByOffsetO…
Inside DolphinScheduler’s May 2026 Release: Better Failover, Stronger Security, and More Reliable Plugins
The May 2026 DolphinScheduler community update can be summarized with two keywords: stability and precision . On one hand, major stability risks such …
Understanding Underfitting and Overfitting: An Introduction
Have you ever trained a model that performed beautifully on your training data but fell apart the moment it saw new data? Or perhaps you built somethi…
Why Your LLM Agent Gives a Different P-Value Every Time (And What to Build Instead)
Hand the same paired before/after dataset (n = 25) to ChatGPT five times. Same prompt: "These are the same subjects measured before and after an inter…
I Built an ML Bitcoin Trading Bot — Then Proved It Had No Edge.
A case study in building crypto trading infrastructure and, more importantly, testing it honestly — including when the honest answer is "no edge." Wha…
A MOGONET-Style Multi-Omics Biomarker Pipeline: Why a Near-Random Graph Net Still Earns Its Place
TL;DR (Quick Answer) This is an honest engineering write-up of a MOGONET-style multi-omics consensus biomarker pipeline built as an internal R&D p…
Algorithmic Trading Pipelines
In This Article Four-Layer Pipeline Architecture WebSocket Ingestion with asyncio Anomaly Detection and Tick Validation The Circuit Breaker Pattern Si…
I Built CausalLens — A Free, Open-Source Causal Impact Calculator for Time Series (5 Methods, Zero Setup)
I want to show you a tool I just open-sourced. It's called CausalLens, and it answers one specific question that most analytics stacks get completely …
The 7 Best Reddit Scrapers in 2026 (Free & Paid, Tested)
Looking for the best way to scrape Reddit posts and comments in 2026? Here's an honest, hands-on comparison of the top Reddit scrapers — including the…
The Paradox of Democratized Software
Everyone can build it. Almost no one can afford to run it at scale. And the companies selling the picks and shovels are about to get undercut by the s…
⚚ I reverse-engineered my mobile operator's APK — then Hermes Agent wrote the executive report
This is a submission for the Hermes Agent Challenge : Write About Hermes Agent // Detect dark theme var iframe = document.getElementById('tweet-205969…
How to Build a Clean Academic Dataset Without Losing Your Mind (or Your Weekend)
The dataset problem nobody talks about.. and the API that quietly solves it. Everyone has an opinion on which model to fine-tune. Nobody talks about w…
Ускоряем и оптимизируем numpy, pandas, scipy и sklearn
С момента публикации статьи на Хабре « Импортозамещаем numpy, pandas, scipy и sklearn » прошло почти три года. В течение этого времени я приостановил …
I Got 96% Recall on LLM Hallucination Detection With No ML Model – Just 50 Lines of Python
Most hallucination detection approaches tell you to train another model. I did not want to do that. I used four statistical signals, a combined score,…