根据随机生成的数量从列表中删除元素

Question

This function should take a list of viruses like [ATCG, GTAC.....] and a mortalityProb (float between 0 and 1) that represents the chance of a virus to die / get deleted from the list. It should return a new list with the remaining viruses. Each of the viruses has an individual chance to die, so with a mortalityProb of say 0.6, there should be around 60% of the viruses remaining.

It should be doable in 2 lines (including def kill(viruses, mortalityProb):) and my line of code using list comprehensions.

def kill(viruses, mortalityProb):
    for i in viruses:
        if random.randint(0, 100) < (mortalityProb * 100):
            del i
    return viruses

This does not quite work, but I can't get a grasp on why.

Answer 1

One way to do this is viruses.remove(i). However, see the various postings on altering a list while you're iterating through it.

You can make this a one-liner; just call random for each virus, and include it if the "saving throw" works.

return [i for i in viruses if random.random() < mortalityProb]

For instance:

>>> viruses = [x for x in range(20)]
>>> [i for i in viruses if random.random() < 0.75]
[0, 1, 3, 6, 7, 9, 10, 11, 12, 13, 15, 17, 18, 19]

BTW, you have your variable misnamed: mortalityProb should describe the chance of the organism dying, not surviving.

Answer 2

Because in the for loop "i' is not actually the element in the list. You have to actually change the viruses list. Something like this may work.

def kill(viruses, mortalityProb):
    for x,i in enumerate(viruses):
        if random.randint(0, 100) < (mortalityProb * 100):
            viruses.pop(x)
    return viruses