Libraries Supporting Composition

Existing libraries supporting composition

There are quite a few open-source libraries that provide functional programming support, including a compose function.

funcy and fn.py are two such libraries that can be found on github.com or installed with pip.

PyMonad

We will concentrate on PyMonad in this section. It provides composition of curried functions (see the PyMonad @curry decorator described earlier in this chapter).

Rather than using a compose function, PyMonad uses a compose operator, *.

Here is how it works.

Example one

Assume that our task is to create an iterator that counts down. We start by creating curried versions of the built-in reversed and range functions as shown below, from line 3 to line 9. Once these functions are defined, composing them is quite neat (line 11).