A good example why immutability by default seems to be the right thing - in Clojure, "seq" would not have been modified by the first filter expression:

    user=> (def seq_ (range 1 11))
    user=> (filter (fn [x] (== (mod x 2) 0)) seq_)
    (2 4 6 8 10)
    user=> (filter (fn [x] (== (mod x 1) 0)) seq_)
    (1 2 3 4 5 6 7 8 9 10)

or more concisely:

    user=> (filter even? seq_)
    (2 4 6 8 10)
    user=> (filter odd? seq_)
    (1 3 5 7 9)

And also an example why it does not work to go and grab one or another desirable feature from a functional language, they need to work together.

> (Which isn't to say that you can't successfully use some functional techniques in Python. But it's best done in a measured, pragmatic way.)

A great example how it is done right is Python's numpy package. The people who created that knew about functional languages and APL (which fits nicely in since Python's predecessor ABC had some APL smell). The obviously knew what they were doing, and created a highly usable combination of a general data type and powerful operations on it.