How to generate list of random integers, but only using specified integers? (Python)

Question

This question could be generalized to randomly creating a list of size n, containing pre-specified integers (assuming a uniform distribution). Hopefully it would look like the following:

Perhaps the syntax would look something like

randList([list of integers], size)

which could then produce something along the lines of:

randList([1,-1], 7)
>>> [1,-1,1,-1,-1,-1,1] #(random)

or

randList([2,3,4], 10)
>>> [4,3,4,2,2,4,2,3,4,3] #(random)

I am a bit new to python and everywhere I look it is always returning a range of values between a low and a high, and not specific values. Thanks

A list comprehension would be more idiomatic than a for loop - `[random.choice(seq) for _ in range(10)]` or something, where `seq` is your list of candidate values. — Peter DeGlopper, Sep 29 '15 at 20:38

score 7 · Accepted Answer · answered Sep 29 '15 at 20:38

7

vals = [random.choice(integers) for _ in range(num_ints)]

answered Sep 29 '15 at 20:38

acushner

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score 3 · Answer 2 · answered Sep 29 '15 at 20:40

Here's a fully working example. All you need to do is replace the value of choices with the list of numbers you want to select from and replace range(10) with range(number_of_items_i_want)

import random
choices = list(range(10))
random_sample = [random.choice(choices) for _ in range(10)]

If you want this as a function so that you can reuse it, this would be an easy way to do it:

import random
def random_list(choices, size):
    return [random.choice(choices) for _ in range(size)]

score 1 · Answer 3 · edited May 23 '17 at 11:58

You want to use random.choice, see this SO answer for a discussion.

However, even if you could only do values within a range:

I am a bit new to python and everywhere I look it is always returning a range of values between a low and a high

...You could still do what you want here, just assume the low/high limits to be 0 -> the size of your list, and then with each random int generated in that range, take the number at that index.

How to generate list of random integers, but only using specified integers? (Python)

3 Answers3