Question

how can I make the func. show all the bad values and not just one?

def get_bad_results(person_results):
        for i in person_results:
                if i[1]>i[3] or i[1]<i[2]:
                    return i[0]

test_results = [["White blood cells",8.5,2,7],
                ["Neutrophils",5.3,2.5,5],
                ["Red blood cells", 12.4, 9,15]]

a = get_bad_results(test_results)
print a

show White blood cells

instead of

White blood cells, Neutrophils

Answer 1

As you expect several results per call, it is the best to use a generator function:

def get_bad_results(person_results):
    for i in person_results:
        if i[1]>i[3] or i[1]<i[2]:
            yield i[0]

or a generator expression:

def get_bad_results(person_results):
    return (i[0] for i in person_results if i[1]>i[3] or i[1]<i[2])

so that

test_results = [["White blood cells",8.5,2,7],
                ["Neutrophils",5.3,2.5,5],
                ["Red blood cells", 12.4, 9,15]]

for i in get_bad_results(test_results):
    print i
print list(get_bad_results(test_results))
print ", ".join(get_bad_results(test_results))

gives the output

White blood cells
Neutrophils
['White blood cells', 'Neutrophils']
White blood cells, Neutrophils

For the other function, do

def count_healthy(all_results):
    counter = 0
    for i in all_results:
        if len(list(get_bad_results(i))) == 0:
            counter += 1
    return counter

or just

def count_healthy(all_results):
    return sum(1 for i in all_results if len(list(get_bad_results(i))) == 0)

---

Edit:

For many get_bad_results(), turning it into a list could be memory-intensive.

So instead of len(list(get_bad_results(i))) == 0 you could use

def has_results(it):
    """Returns True if the iterator it yields any items."""
    return next((True for _ in it), False)

and then

def count_healthy(all_results):
    return sum(1 for i in all_results if not has_results(get_bad_results(i)))