在python中随机生成具有不同元素的3元组

Question

I am trying to generate 3-tuples (x,y,z) in python such that no two of x , y or z have the same value. Furthermore , the variables x , y and z can be defined over separate ranges (0,p) , (0,q) and (0,r) . I would like to be able to generate n such tuples. One obvious way is to call random.random() for each variable and check every time whether x=y=z . Is there a more efficient way to do this ?

Answer 1

You can write a generator that yields desired elements, for example:

def product_no_repeats(*args):
    for p in itertools.product(*args):
        if len(set(p)) == len(p):
            yield p

and apply reservoir sampling to it:

def reservoir(it, k):
    ls = [next(it) for _ in range(k)]
    for i, x in enumerate(it, k + 1):
        j = random.randint(0, i)
        if j < k:
            ls[j] = x
    return ls

xs = range(0, 3)
ys = range(0, 4)
zs = range(0, 5)

size = 4

print reservoir(product_no_repeats(xs, ys, zs), size)