What is the functional way of printing items from range in one line?

Question

for i in range(0,30,3):
    print(i)

What is the functional style of the imperative loop above?

lambda x: print(x), range(0,30,3)

Well, you could choose to call it out and I'll close this question and delete my answer. — cs95, Oct 26 '17 at 11:14
@cᴏʟᴅsᴘᴇᴇᴅ, no i want u to get 5 points for ur answer! ty — ERJAN, Oct 26 '17 at 11:16
@inxoy Technically, `y = list(range(...))` works equally well and is more succinct. — cs95, Oct 26 '17 at 11:17
@Silencer Just, no. Don't encourage the use of list comprehensions for side effects. — cs95, Oct 26 '17 at 11:23
@cᴏʟᴅsᴘᴇᴇᴅ Why? It's just ok for me to quick print items. — Kinght 金, Oct 26 '17 at 12:44
@Silencer https://stackoverflow.com/questions/5753597/is-it-pythonic-to-use-list-comprehensions-for-just-side-effects — cs95, Oct 26 '17 at 12:45
@cᴏʟᴅsᴘᴇᴇᴅ Thank you for correct me, I'll use it just for debuging ... — Kinght 金, Oct 26 '17 at 12:59

score 6 · Accepted Answer · answered Oct 26 '17 at 11:11

A lambda isn't necessary here. Just use the * unpacking operator.

In [163]: print(*range(0, 30, 3))
0 3 6 9 12 15 18 21 24 27

If you want them printed in separate lines, that's doable too.

In [164]: print(*range(0, 30, 3), sep='\n')
0
3
6
9
12
15
18
21
24
27

score 0 · Answer 2 · answered Oct 26 '17 at 11:14

0

if you are using python 2.x you'll need future import:

from __future__ import print_function #dont't need this for python 3.x
print(*range(0,30,3), sep='\n')

answered Oct 26 '17 at 11:14

zipa

score 0 · Answer 3 · answered Oct 26 '17 at 11:19

0

The functional way of doing things is mapping collections to functions

map(print, range(30))

However, because in python map returns a generator, you need to somehow iterate it, which you can do by converting it to a list

list(map(print, range(30)))

answered Oct 26 '17 at 11:19

blue_note

1

Realise that this is called "producing side effects" and generates a list of `[None, None, None, ...]`. This is generally discouraged and reduces readability. – cs95 Oct 26 '17 at 11:20
@cᴏʟᴅsᴘᴇᴇᴅ: Indeed. However, `print` inherently is used for its side effects. In a pure functional style, it wouldn't exist. In general however, given a pure function, this would be the way. – blue_note Oct 26 '17 at 11:22
Yes, but you don't use `map` to exploit that? – cs95 Oct 26 '17 at 11:23
I just wanted to give an example of mapping. Not saying it should be done this way. A simple for loop would be the clearest way in this case. – blue_note Oct 26 '17 at 11:26

3 Answers3