Sorting with keys and lambda

sorted() and .sort() accept a key function that turns each item into the value to sort by. A lambda is a tiny one-line function without a name: lambda s: s["mag"] takes an item and returns its magnitude. Add reverse=True for largest first. min() and max() accept the same key.

How it reads

• key= is called once per item; the list is ordered by what it returns
• lambda s: s["mag"] is the same as a small def that returns s["mag"]
• Built-ins like len can be keys too: key=len

Cloud tip: To sort by two things, return a tuple: key=lambda p: (p["team"], p["score"]).