How do I select a random integer from list, different from previous?

Question

So I have a list with integers like this:

list = [1, 2, 3, 4, 5, 6, 7, 8, 9]

And I want to choose random integer from it with choice:

item = random.choice(list)

But how do I make sure the next time I do this, it is different item? I don't want to remove items from my list.

You can use `random.sample()`. See this [link](http://stackoverflow.com/questions/22842289/python-generate-n-unique-random-numbers-within-a-range) — Amal Rajan, Jul 29 '16 at 10:15
It's a bit annoying when the question gets closed whilst you're coding a solution. I've posted an answer here if you still need it: https://repl.it/ChS5 — logic-unit, Jul 29 '16 at 10:27

Lynn · Answer 1 · 2016-07-29T10:24:42.950

2

If you want n different random values from a list, use random.sample(list, n).

edited Jul 29 '16 at 10:24

answered Jul 29 '16 at 10:13

Lynn

10,425
43
75

1

Sorry I sayed this badly, but I need the item to be different every time, not just different from last item – mahifoo Jul 29 '16 at 10:15
1

@mahifoo: I see. What about if you run out of items in the list? – Lynn Jul 29 '16 at 10:16
@Lynn The list has many items and I only need few of them. It won't run out – mahifoo Jul 29 '16 at 10:17
ramdom.sample() worked good, thanks – mahifoo Jul 29 '16 at 10:23

L3viathan · Answer 2 · 2016-07-29T10:46:50.823

If you need them all anyways and just want them in a random order (but you don't want to change your list), or if you don't have an upper bound on how many items you want to sample (apart from the list size):

import random
def random_order(some_list):
    order = list(range(len(some_list)))
    random.shuffle(order)
    for i in order:
        yield some_list[i]

my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9]

for item in random_order(my_list):
    ... # do stuff

Alternatively, you can use it like this:

order = random_order(my_list)
some_item = next(order)
some_item = next(order)
...

score 0 · Answer 3 · answered Jul 29 '16 at 10:25

Create a generator that checks from previous generated choice:

import random
def randomNotPrevious(l):
    prev = None
    while True:
        choice =  random.choice(l)
        if choice != prev:
            prev = choice
            yield choice

>>> l = [1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> randomLst = randomNotPrevious(l)
>>> next(randomLst)
1
>>> next(randomLst)
5
>>> next(randomLst)
3
>>> next(randomLst)
6
>>> next(randomLst)
5

How do I select a random integer from list, different from previous?

3 Answers3