Python

One asks whether two names point at the same object, the other asks whether the values match. Plus why small numbers seem to break the rule.

Assignment does not copy. A shallow copy copies one level. Here is exactly where the line falls and what copy.deepcopy does about it.

Number formats, alignment, the equals sign debug trick, dates and literal braces. The formatting cheatsheet with real output.

The syntax, filtering, nesting, dict and set versions, and when a generator expression is the better choice.

A decorator is a function that takes a function and returns a new one. Build one from scratch, then see why functools.wraps matters.

A list used as a default argument is created once, not once per call. Here is what that looks like when it goes wrong, and the one line fix.

What the star and the double star actually do, the order the parameters have to be in, and how to pass arguments straight through to another function.