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

Composite design

The common mathematical notation for a composite function looks as follows:


The idea is that we can define a new function, 

, that combines two other functions,



Python's multiple-line definition of a composition function can be done through the following code:

def g(x):

The resulting function can be essentially equivalent to

 . The f_deco() decorator must define and return the composite function by merging an internal definition of f() with the provided g()

The implementation details show that Python actually provides a slightly more complex kind of composition. The structure of a wrapper makes it helpful to think of Python decorator composition as follows:

A decorator applied to some application function, 

, will include a wrapper function,

, that has two parts. One portion of the wrapper, 

, applies to the arguments of the wrapped function,

, and the other portion, 

 , applies to the result of the wrapped function.

Here's a more concrete idea, shown...