我的质数列表中的3在哪里被追加？

Question

我可以理解如何在3之后添加其他质数，因为(x%y != 0)，但对于for循环的第一次迭代，x%y似乎等于0。那么，它怎么会被添加到我的主要列表中呢？

def count_primes(num):
# edge case: 1 and 0 are not prime numbers
    if num < 2:
        return 0

# create prime list, check length to find amount of primes up to input num
# insert 2 bc it is only even prime number. Allows use of step in range to only iterate odds
    primes = [2]

# create variable that holds prime candidates starting after 2
    x = 3

# proceed into loop if prime candidate is less than or equal to input number
    while x <= num:
# cycle through odd numbers up to input number
        for y in range(3,x,2):
            if x%y == 0:
                x += 2
                break
        else:
            primes.append(x)
            x += 2
    return primes

Answer 1

当x为3时，range(3,x,2)是一个空范围-因此不会对该数字执行%测试。

-jasonharper的comment