Lists

A list is Python's array

Swift has var names: [String] = ["Ana", "Ben"]. Python's version is a list, and it's even less ceremony:

walkers = ["Ana", "Ben", "Cleo"]

No type annotation, no [String] — a list can technically hold mixed types, but in PawWalk code you'll keep each list's items the same shape (all walker names, all bookings, etc.), exactly like you did in Swift.