打印素数的初级版本

a = int(input("请输入一个数字："))
if a == 1 or a == 2:
    print(a," 是素数")
else:
    for n in range(2,a):
        if a % n == 0:
            print(a," 不是素数")
            break
    else:
        print(a," 是素数")