Generating a single random integer in Python

Question

I want to generate a unique random integer for the variable SEED. This code is part of a bigger script that is going to run multiple times and output each time, so feeding SEED with a non-duplicate random integer is important. Also, I tried random.sample and such that return lists/sequence not an integer, but this is not the case here because of the following line using torch.

SEED = random.randint(1, 1000)
random.seed(SEED)
np.random.seed(SEED)
torch.manual_seed(SEED)
torch.cuda.manual_seed(SEED)
torch.backends.cudnn.deterministic = True

I need it to generate a duplicate free random integer, but it does not! — Mahan Agha Zahedi, Jun 25 '21 at 18:48

score 3 · Answer 1 · answered Jun 25 '21 at 18:48

3

You can also use time.time():

import time
SEED = int(time.time())

This is technically unique since it'll be a different timestamp every time you run the code.

answered Jun 25 '21 at 18:48

enzo

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even if I run it inside a loop that lasts around 3 hours? – Mahan Agha Zahedi Jun 25 '21 at 18:55
I don't know exactly what is your use case, but why don't you initialize `SEED` outside the loop? – enzo Jun 25 '21 at 18:57
because if I do so it's going to run the loops with the same `SEED`. I need to run each iteration with a unique `SEED`. – Mahan Agha Zahedi Jun 25 '21 at 19:12
What if I need to generate multiple unique seeds within 1 second? Your method will fail. – Shaun Han Apr 22 '22 at 16:14

score 1 · Answer 2 · answered Jun 25 '21 at 18:44

1

As an ultimate solution cast UUID to long integer from here:

import uuid
uuid.uuid4().int & (1<<64)-1
9518405196747027403L

answered Jun 25 '21 at 18:44

Digoya

121
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how can I edit this to get up to 3 digits? – Mahan Agha Zahedi Jun 25 '21 at 18:51
1

uuid.uuid4().int & (1<<10)-1 – Digoya Jun 25 '21 at 18:54
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@MahanAghaZahedi while a UUID is guaranteed to be unique, a 3-digit piece of it is not. In fact any manipulation will lose the uniqueness guarantee. – Mark Ransom Jun 25 '21 at 21:42

DomasAquinas · Accepted Answer · 2021-06-26T02:47:25.450

1

Perhaps this is a little too brute-force, but randomly popping integers out of a list of integers seems to work:

min_seed = 1
max_seed = 1000
seed_list = [*range(min_seed, max_seed+1)]

n_repetitions = 300  # or whatever, as long as n_repetitions < len(seed_list)
for repetition in range(0, n_repetitions):
    seed = seed_list.pop(random.randint(min_seed,len(seed_list)))

Since the integers get popped out of the list as they're used as seeds, there won't be repeats.

edited Jun 26 '21 at 02:47

answered Jun 25 '21 at 18:51

DomasAquinas

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1
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Lengthy but functional but that's all that matters! Thanks! – Mahan Agha Zahedi Jun 25 '21 at 18:56
Why the list comprehension instead of just `list(range(...))`? – Mark Ransom Jun 25 '21 at 21:47
No real reason, just cranking out code. :^) I prefer the comprehension just because it conveys a bit more intention, at least to me - it reads as "I'm building a list" rather than "I want this other thing to be a list." – DomasAquinas Jun 25 '21 at 23:44
For what it's worth, `timeit` is telling me that `list(range(...))` is considerably faster. For 10,000 repetitions of each, the comprehension takes 0.198 sec, and `list(range(...))` 0.0855 sec. So there, a counterargument against my original way! – DomasAquinas Jun 25 '21 at 23:50
Update - `timeit` reveals a yet speedier way! `[range(...)]` clocks in at 0.00366 sec for 10,000 repetitions! I like that one... I'll edit it into the answer. Thanks for inspiring the hunt, @MarkRansom! – DomasAquinas Jun 26 '21 at 02:21
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`[range(a, b)]` creates a list with length 1, but `list(range(a, b))` creates a list with length b - 1 - a. – enzo Jun 26 '21 at 02:27
@enzo that means the `pop` won't work on a list built that way. Good catch. – Mark Ransom Jun 26 '21 at 02:34
@enzo - thanks! Forgot the unpacking. It's slower than the wrong version (rats), but still the fastest I've tried (0.0775 sec). Ought to be `[*range(...)]`. Ugh, typos... ;^) – DomasAquinas Jun 26 '21 at 02:46

Generating a single random integer in Python

3 Answers3