Even with named functions, Python's use of global functions instead of methods for iterators force you to read the expression from the inside out. I think Lisp languages nailed this with their threading macros, which allow natural left-to-right reading, but Ruby's strategy is better than Python's, too, while maintaining very similar syntax.

    ;; clojure
    (let [begins-with-a #(.startsWith % "a")
          foo #(do-some-stuff-with %)]
      (-> words (filter begins-with-a) (map foo))))

    # ruby
    words.filter { |e| e.start_with?(?a) }.map { |e| foo(e) }

It doesn't really make sense for things like `len` and `map` to be global functions in object-oriented languages.