欧拉计划 7

前六个质数是2,3,5,7,11和13，其中第6个是13.

第10001个质数是多少？

#import math
#
#
#def is_prime(x):
#    if x % 3 == 0 or x % 5 == 0 or x % 7 == 0:
#        return False
#    x_sqrt = int(math.sqrt(x))
#    l = [2]
#    l.extend(range(3, x_sqrt + 1, 2))
#    for i in l:
#        if x % i == 0:
#            return False
#    return True
#    
#
#n_prime = 10001
#prime = 7
#prime_num = 4
#while prime_num < n_prime:
#    prime += 2
#    if is_prime(prime):
#        prime_num += 1
#print(prime)


def is_prime(x):
    """ 是否为质数 """
    for i in prime_list:
        if x % i == 0:
            return False
        if i ** 2 > x:
            break
    return True


n_prime = 10001
prime_list = [2, 3, 5, 7]
prime = prime_list[-1]
while len(prime_list) < n_prime:
    prime += 2
    if is_prime(prime):
        prime_list.append(prime)
print(prime)