Book Image

Functional Python Programming. - Second Edition

Book Image

Functional Python Programming. - Second Edition

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

Starmapping with operators

The itertools.starmap() function is a variation on the map() higher-order function. The map() function applies a function against each item from a sequence. The starmap(f, S) function presumes each item, i, from the sequence, S, is a tuple, and uses f(*i). The number of items in each tuple must match the number of parameters in the given function.

Here's an example:

>>> d = starmap(pow, zip_longest([], range(4), fillvalue=60))  

The itertools.zip_longest() function will create a sequence of pairs, such as the following:

[(60, 0), (60, 1), (60, 2), (60, 3)]

It does this because we provided two sequences: the [] brackets and the range(4) parameter. The fillvalue parameter will be used when the shorter sequence runs out of data.

When we use the starmap() function, each pair becomes the argument to the given function. In this case, we provided the operator.pow() function, which is the ** operator. This expression calculates values for [60**0, 60**1, 60**2, 60**3...