CODEWITHSUNDEEP
javascriptpythonrandommersenne-twister
Pikamander2
Pikamander2

Reputation: 8319

How can I generate the same random number in JavaScript and Python?

In Python, if I use this code:

import random
random.seed(123)
print(random.random())

The first random number will always be 0.052363598850944326, since I'm giving it the same seed every time I run the program.

JavaScript doesn't have a built-in way to use seeds. I've tried out a JavaScript script called mersenne-twister.js, since that's the type of PRNG that Python uses. But even if I use the same seed, I get a different result than I do in Python.

var m = new MersenneTwister(123);
m.genrand_int32();

That code will always return 0.6964691872708499 the first time that it's run.

How can I use a given seed to get the same random number in both Python and JavaScript?

Upvotes: 2

Views: 3397

Answers (2)

fbparis
fbparis

Reputation: 920

If you don't need a cryptographically secure pseudorandom number generator, you could use something like this, using the decimals of sinus function.

In python:

import math
def simple_random(precision=10000):
    i = 1
    while 1:
        x = math.sin(i) * precision
        yield x - math.floor(x)
        i += 1

In Javascript:

var i = 1;
function simple_random(precision=10000) {
    x = Math.sin(i++) * precision;
    return x - Math.floor(x);
}

If you want to vary seeds, you could use something like sin(a * i + b) rather than sin(i) or a * sin(i + b), it's up to you to find something good enough.

Upvotes: 0

Nitsew
Nitsew

Reputation: 3662

This library/plugin worked for me when I compared the Python output to the JavaScript output.

https://github.com/davidbau/seedrandom

Upvotes: 1

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