Functional Programming in Python 🐍

About me

Riccardo aka @entropiae

Python in the streets
Erlang/Elixir (currently) in the sheets

(almost) every developer has its own idea about functional programming.

First-class functions

Higher-order functions

Recursion instead of iteration

Focus on Tail Call Optimization

Immutable data structures

Lazy evaluation

                            len([1, 1/0, '3']) == 3

Emphasis on what is done, not on ~~how~~ is done

(Mathematical) functions

Pure functions

No side effects

Perfectly pure, almost useless

Practicality beats purity.

Referential transparency

Memoization

No order constraint

Full support for Multi{core, cpu, node} archs

Compiler optimization

Python is not, by design, a FP language

However..

..coz everything is an object..

..we have first-class functions! 🎉

1994: higher-order functions were introduced in Python

map: transform a collection

map(lambda x: x + 1, [1, 2, 3]) == [2, 3, 4]

filter: remove elements from a collection

filter(lambda x: x % 2 == 0, [1, 2, 3]) == [2]

reduce: recursively apply an operation on a collection

reduce(lambda x, y: x + y, [1, 2, 3]) == 6

The cornestone of higher-order functions

map() and filter() could be replaced with a list comprehension

There should be one - and preferably only one - obvious way to do it.

GvR doesn't like them 😕

It was proposed to remove them from Python 3

More functions were build on these building blocks

functools, itertools