Cryptographically random numbers

[Tuvas]

Okay, I'm working on devoloping a simple, cryptographically secure
number, from a range of numbers (As one might do for finding large
numbers, to test if they are prime). My function looks like this:

def cran_rand(min,max):
    if(min>max):
        x=max
        max=min
        min=x
    range=round(log(max-min)/log(256))
    if range==0:
        range=1
    num=max+1
    while(num>max):
        num=min+s2num(urandom(range))
    return num

Any comments on this? I think it should hold up to a test, it seems to
work alright. Thanks!