#简单判断是否成年
age=19
if age>18:
    print("成年了")
else:
    print("未成年")
#输出：成年了

#根据红绿灯执行
lights="blue"
if lights == "red":
    print("stop")
elif lights == "green":
    print("go")
else:
    print("开心就好")
#输出：开心就好

#模拟系统登录
yonghuming=‘admin‘
mima=‘123‘
username=input(‘请输入用户名:‘)
password=input(‘请输入密码:‘)
if username == yonghuming and password == mima:
    print(‘正在进入系统,请稍后‘+‘.‘*20)
elif username!=yonghuming and password!=mima:
    print(‘账号和口令都不正确，请重试！‘)
elif username!=yonghuming:
    print(‘账号不正确，请重试！‘)
else:
    print(‘口令不正确，请重试！‘)
    print(‘结束‘)