A silly deterministic shuffle.

README.md

Just a note-to-self to prevent me from reinventing the wheel again.

A shuffle that always produces a predictable output.

e.g.

>>> x = [0,1,2,3,4,5,6,7,8,9]
>>> dshuffle(x)
[7, 8, 1, 5, 3, 4, 2, 0, 9, 6]

>>> dshuffle(x)
[7, 8, 1, 5, 3, 4, 2, 0, 9, 6]

>>> dshuffle(x)
[7, 8, 1, 5, 3, 4, 2, 0, 9, 6]

Update the state to get new predictable values:

>>> rnd = Random(1) # different seed
>>> rnd_state = rnd.getstate()
>>> x = [0,1,2,3,4,5,6,7,8,9]
>>> dshuffle(x)
[6, 8, 9, 7, 5, 3, 0, 4, 1, 2]

>>> dshuffle(x)
[6, 8, 9, 7, 5, 3, 0, 4, 1, 2]

>>> dshuffle(x)
[6, 8, 9, 7, 5, 3, 0, 4, 1, 2]

dshuffle.py

from random import Random
rnd = Random(0)
rnd_state = rnd.getstate()

def dshuffle(i, sort=True):
    rnd.setstate(rnd_state)
    t = type(i)
    x = list(i)
    if sort:
        try:
            x = sorted(x)
        except:
            x = sorted(x, key=str)
    rnd.shuffle(x)
    if t == str:
        return "".join(str(_) for _ in x)
    try:
        return type(t.__name__, (t,), {})(x)
    except:
        if t.__name__ == "generator":
            return iter(x)
        else:
            return x