python用筛法输出指定范围素数个数

 1 import time
 2 stime = time.time()
 3 def q(n):
 4     is_prime = {x:True for x in range(n+1)} # 生成一个n个元素的字典 key设置为0-n+1 值设置为True
 5     del is_prime[0] #删除0 
 6     for c in (2,3,5,7): 
 7         for z in range(2,int(n/2)):
 8             try:
 9                 index = c * z
10                 if index > n:
11                     pass
12                 else:
13                     print(index)
14                     del is_prime[index]
15             except:
16                 pass
17     print(len(is_prime))
18 
19 q(1000000)
20 etime = time.time() - stime
21 ftime = str(etime)
22 print('耗时:'+ftime)