为什么我的程序重复打印列表？

Question

我正在为欧拉计划第 7 题编写程序，试图找到第 10001 个素数。我改编了一个我已经拥有的脚本，该脚本可以找到所有素数直到任何数字。它运作良好。但现在我有一个问题。我的代码重复列表。

881, 883, 887, 1, 2, 3, 5, 7, 11, 13, 17, 19

那是我代码的大致中间部分。

max = int(input("What is your max no?: "))
primeList = []

while len(primeList) <= 10001:
for x in range(1, max + 1):
    isPrime = True
    for y in range (2 , int(x ** 0.5) + 1):
        if x % y == 0:
            isPrime = False
            break

    if isPrime:
        primeList.append(x)


print(primeList)

这是什么原因造成的？我应该从空白开始 canvas 而不是编辑旧脚本吗？

Answer 1

每次你找到一个质数，你就把它添加到 primeList 中，所以最后一行被要求打印一个列表。如果你想要最后一个元素，你可以：

print primeList[-1]

Answer 2

为了好玩我也解决了这个问题：

# Test only odd numbers because we know the only even prime is 2
oddprimes = [3]
n = 3
# when we have 10000 oddprimes we will have a total of 10001 primes: [2] + oddprimes
while len(oddprimes) < 10000:
    n += 2 # advance to the next odd number
    maxfactor = int(n ** 0.5) + 1
    # only need to check prime factors
    for prime in oddprimes:
        if n % prime == 0:
            # it's not prime, stop looking
            break 
        elif prime >= maxfactor:
            # if we're checking prime factors >= sqrt(n)+1 then it's prime
            oddprimes.append(n) 
            break

print oddprimes[-1] # the 10000th odd prime which is the 10001st prime

为什么我的程序重复打印列表？

Why does my program repeat print lists?

python

primes

python-2.7