4 posts.
Almost everyone optimises the wrong thing. Measure with cProfile and timeit instead, learn to read the output, and use the two facts that explain most slow Python: membership tests that are O(n) inside a loop, and Amdahl's law, which caps how much any one fix can buy you.
Binary is just place value with twos instead of tens. Learn to convert binary to decimal and back in your head, then flip the bits yourself in an interactive 8-bit converter.
A short, safe Python script that batch-renames files (photos, invoices, downloads) with a dry run first, so you see every change before it happens. Copy-paste code and an interactive previewer.
Regular expressions look like line noise until you learn about a dozen symbols. The essentials, five patterns you'll actually use, and a live tester to experiment with in your browser.