Gain insights into functional programming in Python, learn about functions as objects, recursion, closures, and generators, and discover how to confidently apply these concepts to your projects.

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The functional programming paradigm can be a powerful tool, especially as it can be integrated seamlessly with procedural and object-oriented code in Python. 

In this course, you’ll learn what functional programming is, how it’s used, and the features of Python that support it. To start, you’ll learn how functions act as objects, the role of mutability, and how to perform recursion. 

In the latter half of the course, you’ll focus on closures, iterables & iterators, generators, and more. Throughout the course will be three exams which will test your understanding and really drive home what you’ve learned.  

By the end, you’ll have a new programming paradigm to add under your belt and have the confidence to start using functional programming in your own projects.

Learn Functional Programming in Python

We have mentioned several libraries in other sections of this course. This chapter tells you where to find them and lists further areas to explore.


# itertools

`itertools` is a standard Python library – it is part of Python and doesn’t need any extra installation.

It contains a number of useful extra functions for iteration. Here are some of the highlights; refer to the documentation on python.org for a full list.


## Infinite iterators

These are iterators that go on forever.

### `count`

`count(start, [step])` produces an infinite series of incrementing values with an initial start value. 

For example:

```python
count(0) # Creates 0, 1, 2 ...
```

It behaves like `range` but with the end value set to infinity. There is an optional step value:

```python
count(5, 2) # Creates 5, 7, 9 ...
```

### `repeat`

`repeat(x, [n])` produces an infinite series of the value, `x`, repeated over and over. The optional value, `n`, will cause the sequence to stop after `n` iterations.

### `cycle`

`cycle(it)` creates an infinite series by repeating the values in `it` (an iterable) indefinitely.

For example:
```python
cycle([1, 2, 3]) # Create 1, 2, 3, 1, 2, 3, 1, 2, 3...
```

You can try out these iterators in the code widget below.

Learn about functions that the itertools library provides for iteration.

Introduction

Functions as Objects

Mutability

Recursion

Functional Programming in Python - Exam 1

Closures

Iterators

Transforming Iterables

Reducing Iterables

Functional Programming in Python - Exam 2

Comprehensions

Generators

Partial Application and Currying

Functors and Monads

Functional Programming in Python - Exam 3

Useful Libraries

Conclusion

Itertools

itertools

Infinite iterators

`count`