Book Image

Functional Python Programming - Second Edition

By : Steven F. Lott
Book Image

Functional Python Programming - Second Edition

By: Steven F. Lott

Overview of this book

If you’re a Python developer who wants to discover how to take the power of functional programming (FP) and bring it into your own programs, then this book is essential for you, even if you know next to nothing about the paradigm. Starting with a general overview of functional concepts, you’ll explore common functional features such as first-class and higher-order functions, pure functions, and more. You’ll see how these are accomplished in Python 3.6 to give you the core foundations you’ll build upon. After that, you’ll discover common functional optimizations for Python to help your apps reach even higher speeds. You’ll learn FP concepts such as lazy evaluation using Python’s generator functions and expressions. Moving forward, you’ll learn to design and implement decorators to create composite functions. You'll also explore data preparation techniques and data exploration in depth, and see how the Python standard library fits the functional programming model. Finally, to top off your journey into the world of functional Python, you’ll at look at the PyMonad project and some larger examples to put everything into perspective.
Table of Contents (22 chapters)
Title Page
Packt Upsell

Building higher-order functions with callables

We can define higher-order functions as callable classes. This builds on the idea of writing generator functions; we'll write callables because we need statement features of Python. In addition to using statements, we can also apply a static configuration when creating the higher-order functions.

What's important about a callable class definition is that the class object, created by the class statement, defines a function that emits a function. Commonly, we'll use a callable object to create a composite function that combines two other functions into something relatively complex.

To emphasize this, consider the following class:

from typing import Callable, Optional, Any

class NullAware:
    def __init__(
            self, some_func: Callable[[Any], Any]) -> None:
        self.some_func = some_func
    def __call__(self, arg: Optional[Any]) -> Optional[Any]:
        return None if arg is None else self.some_func(arg)

This class is used to...