列出所有素数以及素数个数，使用 num/2+1 方式减少计算量

#!/usr/bin/python
# -*- coding: UTF-8 -*-
lower = int(input("输入区间最小值: "))
upper = int(input("输入区间最大值: "))
n = 0
for num in range(lower, upper + 1):
    if num >1:
        for i in range(2,num/2+1):
            if num%i ==0:
                break
        else:
            print (num)
            n += 1
print lower,'到',upper,'素数总数为',n

参考方法：

#!/usr/bin/python
# -*- coding: UTF-8 -*-

for i in range(2,100):
    if 0  not in [i%n for n in range(2,i)]:
        print i,

python2 与 python3实测通过：

# -*- coding: UTF-8 -*-

a = []
for i in range(2, 101):
    for j in range(2, 101):
        if i * j <= 100:
            a.append(i * j)
b = set(a)
c = set(range(1, 101))
d = c - b
print(d)