This week, I learned:
nl FILE and cat -n FILE add line numbers to files, but nl skips blank lines by default, cat doesn't.rtk for 2 months, I'm slightly downgrading it. It saves tokens but agents mess up shell commands when using it. It's still probably a net saving, so I've changed my AGENTS.md from "Always prefix with rtk" to "Prefix supported, high-output commands with rtk... skip for bash builtins, pipes, loops, etc."str.casefold(). It performs more comprehensive Unicode caseless matching than lower(); 'Straẞe'.casefold() becomes 'strasse'. (🟢 Unicode case-folding is standardized.) contextlib.closing(x) calls x.close() when its context exits. (⚪) In a dataclass, use x: list = dataclasses.field(default_factory=list), not a mutable literal default. (⚪)