I know how to shuffle a list of elements. But hos should I do if I want to shuffle all the elements between two specific elements.
import random
x = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
random.shuffle(x)
print(x)
I tried following way, but it produce "None".
import random
x = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
random.shuffle(x[2:5]) # need an output like this e.g: [1, 2, 4, 5, 3, 6, 7, 8, 9, 10]
print(x)
But it didnt work. Thanks for the help.
shuffle works in-place, so you need to take a slice of your list, shuffle it, and then slice-reassign to the original list.
>>> from random import shuffle
>>>
>>> x = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Create a shuffled list shuffled.
>>> shuffle_range = slice(2, 5)
>>> shuffled = x[shuffle_range]
>>> shuffle(shuffled)
Reassign the shuffled part to a slice of the original list:
>>> x[shuffle_range] = shuffled
>>>
>>> x
[1, 2, 4, 5, 3, 6, 7, 8, 9, 10]
I created the slice(2, 5) object in order to not repeat myself typing the indices.
x is mutated in-place in this approach, just like you would expect from an ordinary shuffle-operation.
shuffle works in place. So what happens is that your list slice x[2:5] is shuffled, then discarded as it has no reference left.
You'd have to do:
part = x[2:5]
random.shuffle(part)
x = x[:2] + part + x[5:]
This naïve approach which recreates a copy of x. If x is huge and you just shuffle a small part of it, the memory overhead is too much. Commenters suggested to replace the last line by a better slice assignment:
x[2:5] = part