Python：过滤器和生成器

Question

Here is the code:

def _odd_iter():
    n = 1
    while True:
        n = n + 2
        yield n
def _not_divisible(n):
    return lambda x: x % n > 0
def primes():
    yield 2
    it = _odd_iter()
    while True:
        n = next(it) 
        yield n
        it = filter(_not_divisible(n), it)
for n in primes():
    if n < 10:
        print(n)
    else:
        break

1. I want to know what is the process about this practice , i was stuck on the

it = _odd_iter()

and

it = filter(_not_divisible(n), it)

Is the it stored value like list or something?

Answer 1

For the first part, filter() returns a filter object(which is an iterator) and not a list

>>> filter(lambda x : x < 5 , [1,2,3,4,5,6,7,8])
<filter object at 0x7eff8b5922e8>
>>> list(filter(lambda x : x < 5 , [1,2,3,4,5,6,7,8]))
[1, 2, 3, 4]

You can check python docs for more information. This is only in Python3.

The second part is similar. filter() will iterate through the generator and create another iterator which contains the filtered data.