1.循环输出0~10

for i in range(11):
    print(i)

2.循环输出2，10

for i in range(2,11):
    print(i)

3.输出2，5，8，11

for i in range(2,12,3):
    print(i)

4.输出50个*

print('*'*50)

5.求1~50的累加和

sum=0
for i in range(1,51):
    sum+=i
print(sum)

6.用户尽可以登录三次

for i in range(3):
    username = input('用户名:')
    password = input('密码:')
    # 判断输入是否正确
    if username == 'admin' and password == '123456':
        print('用户登录成功')
        break
    print('用户名或密码有误！\n')
else:
    print('用户被锁定')