[duckerude]

map() and filter() being functions means you can run them on any object that implements __iter__(). To make them methods they'd have to be added to each individual type that might want to use them. IIRC Ruby does that using mixins but that takes up a lot of room in the namespace of each type and makes it a little harder to figure out where the methods come from.

The justification for len() is thinner: Guido van Rossum thinks it looks better, and it enforces a consistent name with a consistent meaning (you don't get length methods with different names, or with the right name but strange behavior). Under the hood it just calls obj.__len__(), so it's only the notation that's not OOP.

There are no multi-line lambdas because nobody could come up with an indentation-based syntax for them that Guido van Rossum was happy with.

In short: none of them improved, all of them have reasons, some of those reasons are bad.