Some functional programming techniques in Python

Hi, Habr!
In this article, I would like to talk about what came to Python from functional programming languages. Interested please under the cat.

List generators

It's easy and simple: instead of

l = [] for x in range(10): if x % 2 == 0: l.append(x) 

we are writing

 l = [x for x in range(10) if x % 2 == 0] 

Short and clear.

 let l = [x | x <- [0..10], x `mod` 2 == 0] 

Lambda

Suppose we write a graphical interface and we have a function button (** kwargs), where valid named arguments are: text is for text, width is for width, height is for height, and command is for callback function:

 def callback(event): print("Button pressed") button(text="Press me", width=32, height=16, command=callback) 

Pay attention to how small our callback is, can it really be pushed through with an argument? Can! We will help lambda:

 button(text="Press me", width=32, height=16, command=lambda x: print("Button pressed")) 

Clean and easy!

 map (\x -> x+1) [1..10] 

 map(lambda x: x+1, [x for x in range(1, 10)]) 

Carring

Currying (currying) is when we pass one or more arguments to an old function in order to get a new one that accepts the rest (thanks to AnutaU for a more precise definition). For example: print is a function (I use Python 3), it has a named argument end - the end of the line, by default it is "\ n". I want not to move to a new line, then I write

 print(str, end="") 

Let's do a printf function that will not move to a new line.

 def printf(*args, **kwargs): kwargs["end"] = "" print(*args, **kwargs) 

Sloppy, it is possible and easier:

 from functools import partial printf = partial(print, end = "") 

Here it is, currying - we say we want exactly the same but with pearl buttons print function, but so that end is "". It's simple.

 let plusTwo = (+2) 

I have everything, if you know what else there is in Python from the functional area - please in the comments.
Questions and reviews there too.