🔒 Mimic Python's Random choices in JavaScript

[shrewd charm]

Hey! I'm not sure if it stays Python related but here's a simple short script I made to make choices based on a seed in Python:

import random


if __name__ == "__main__":
    seed: str = "ARandomSeed"
    results: int = 3
    random.seed(seed)
    fields = list(range(25))
    res = []
    for _ in range(results):
        field = random.choice(fields)
        res.append(field)
        fields.remove(field)
    res.sort()
    print(res)

The thing I'd like to do is reproduce the random choices in JavaScript, I'd like the two different program to output the exact same results if they have the same seed!

[forest sparrow]

@shrewd charm

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[ionic heath]

use random.sample instead of random.choice in a loop

then you don't have to remove stuff

!e ```py
import random

if name == "main":
seed = "ARandomSeed"
results = 3
random.seed(seed)
res = sorted(random.sample(range(25), k=results))
print(res)

[forest sparrow]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

[7, 13, 14]

[shrewd charm]

!e

import random


if __name__ == "__main__":
    seed: str = "ARandomSeed"
    results: int = 3
    random.seed(seed)
    fields = list(range(25))
    res = []
    for _ in range(results):
        field = random.choice(fields)
        res.append(field)
        fields.remove(field)
    res.sort()
    print(res)

[forest sparrow]

:white_check_mark: Your 3.12 eval job has completed with return code 0.

[7, 14, 15]

[ionic heath]

ah wait

[shrewd charm]

Output aren't the same if I use random.sample!

[ionic heath]

interesting

so you gotta look in the implementation

all the python source code is on github

[twin meadow]

I think this is pretty tricky to achieve in JavaScript since the builtin Math.random function isn't very standardized. You may want to consider using an implementation of the algorithm python uses to generate it's random numbers (the Mersenne Twister) although I doubt you can achieve true cross-platform uniformity in generating your randomness

[twin meadow]

random.sample will return k unique elements as opposed to OP's implementation which may return non-unique results

[shrewd charm]

I already tried something:

    class MersenneTwister {
        constructor() {
            this.N = 624;
            this.M = 397;
            this.MATRIX_A = 0x9908b0df;
            this.UPPER_MASK = 0x80000000;
            this.LOWER_MASK = 0x7fffffff;

            this.mt = new Array(this.N);
            this.mti = this.N + 1;
        }

        init_genrand(s) {
            this.mt[0] = s >>> 0;
            for (this.mti = 1; this.mti < this.N; this.mti++) {
                let s = this.mt[this.mti - 1] ^ (this.mt[this.mti - 1] >>> 30);
                this.mt[this.mti] = (((((s & 0xffff0000) >>> 16) * 1812433253) << 16) +
                    (s & 0x0000ffff) * 1812433253) + this.mti;
                this.mt[this.mti] >>>= 0;
            }
        }

        init_by_array(init_key) {
            let key_length = init_key.length;
            this.init_genrand(19650218);
            let i = 1;
            let j = 0;
            let k = this.N > key_length ? this.N : key_length;
            for (; k; k--) {
                let s = this.mt[i - 1] ^ (this.mt[i - 1] >>> 30);
                this.mt[i] = (this.mt[i] ^ (((((s & 0xffff0000) >>> 16) * 1664525) << 16) +
                    ((s & 0x0000ffff) * 1664525))) + init_key[j] + j;
                this.mt[i] >>>= 0;
                i++;
                j++;
                if (i >= this.N) { this.mt[0] = this.mt[this.N - 1]; i = 1; }
                if (j >= key_length) { j = 0; }
            }
            for (k = this.N - 1; k; k--) {
                let s = this.mt[i - 1] ^ (this.mt[i - 1] >>> 30);
                this.mt[i] = (this.mt[i] ^ (((((s & 0xffff0000) >>> 16) * 1566083941) << 16) +
                    ((s & 0x0000ffff) * 1566083941))) - i;
                this.mt[i] >>>= 0;
                i++;
                if (i >= this.N) { this.mt[0] = this.mt[this.N - 1]; i = 1; }
            }
            this.mt[0] = 0x80000000;
        }

        genrand_int32() {
            let y;
            let mag01 = [0x0, this.MATRIX_A];

            if (this.mti >= this.N) {
                let kk;

                if (this.mti === this.N + 1)
                    this.init_genrand(5489);

                for (kk = 0; kk < this.N - this.M; kk++) {
                    y = (this.mt[kk] & this.UPPER_MASK) | (this.mt[kk + 1] & this.LOWER_MASK);
                    this.mt[kk] = this.mt[kk + this.M] ^ (y >>> 1) ^ mag01[y & 0x1];
                }
                for (; kk < this.N - 1; kk++) {
                    y = (this.mt[kk] & this.UPPER_MASK) | (this.mt[kk + 1] & this.LOWER_MASK);
                    this.mt[kk] = this.mt[kk + (this.M - this.N)] ^ (y >>> 1) ^ mag01[y & 0x1];
                }
                y = (this.mt[this.N - 1] & this.UPPER_MASK) | (this.mt[0] & this.LOWER_MASK);
                this.mt[this.N - 1] = this.mt[this.M - 1] ^ (y >>> 1) ^ mag01[y & 0x1];

                this.mti = 0;
            }

            y = this.mt[this.mti++];

            /* Tempering */
            y ^= y >>> 11;
            y ^= (y << 7) & 0x9d2c5680;
            y ^= (y << 15) & 0xefc60000;
            y ^= y >>> 18;

            return y >>> 0;
        }

        random() {
            let a = this.genrand_int32() >>> 5; // Upper 27 bits
            let b = this.genrand_int32() >>> 6; // Upper 26 bits
            return ((a * 67108864.0) + b) * (1.0 / 9007199254740992.0);
        }
    }

But it's not working

I mean, it is

But it's not giving the same output as Python

[twin meadow]

they're not the same?

ah

[ionic heath]

no, because they remove the chosen item from their list

therefore it returns unique elements

[twin meadow]

oh oops I didn't notice that

[ionic heath]

i think it's due to the length changing

whereas in sample you don't change the length

[twin meadow]

yeah probably

anyway my guess is that there is some implementation detail which is different from cpython's algorithm and yours

the easiest way to get the same random numbers would probably be to talk to a python server from your javascript and return some random numbers, unless you want to try and debug your pseudo-random number generator 😢

[shrewd charm]

OR

Maybe there’s an API where I could send a python code eval

And use the output in my JavaScript code

[twin meadow]

you could also try that

this seems like an interesting problem so I might try and work on it later when I get back from walking my dog (if I remember)

[shrewd charm]

Keep me updated!

[brave burrow]

You might have some luck with https://pyodide.org/en/stable/

[twin meadow]

I was also thinking about that 😂😂

[forest sparrow]

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