I have seen the knapsack problem show up in quite a few technical interviews. It is one of those problems that feels tricky at first but becomes much clearer once you see the recursive pattern underneath. In this tutorial, I…
Text mining is the process of turning raw, unstructured text into structured data you can count, analyze, and visualize. In Python, a handful of libraries handles the full pipeline — loading text, cleaning it, tokenizing words, removing common filler words,…
Optical Character Recognition lets you extract printed, handwritten, or scanned text from images and convert it into machine-readable data. If you have ever stared at a photograph of a table and dreaded typing all that data into a spreadsheet by…
You are writing a Python program and need to output bracket characters in your output. A user-facing message might need square brackets. A debug statement might need curly braces. The print() function does not make this obvious because brackets also…
The while loop in Python repeats a block of code as long as a condition evaluates to True. You use it when you do not know upfront how many iterations you need. The loop stops the moment the condition becomes…
GitPython is a Python library that lets you interact with Git repositories directly from Python code. You can clone, pull, push, and inspect commits without calling the git command line. This is useful when you need to automate repository operations…
The factorial of a number n is the product of every integer from 1 to n. factorial(5) = 5 * 4 * 3 * 2 * 1 = 120. The operation shows up in probability, permutations, and series expansions. Python…
You have a string and you want to list every possible combination of its characters. The order matters, and each character can either show up in a combination or vanish. That is the subsequence problem. I ran into it first…
Principal component analysis, or PCA in short, is famously known as a dimensionality reduction technique. It has been around since 1901 and is still used as a predominant dimensionality reduction method in machine learning and statistics. PCA is an unsupervised…
Counterfeit detection sounds like a job for the Secret Service. Turns out, it is also a solid machine learning exercise. The fake bills dataset from Kaggle packs 1,400 labeled dollar bills with six geometric measurements. The question is not just…