day2 python全栈学习笔记

1、用户登陆

i=0
while i<3:
    i += 1
    j = 3 - i
    username = input("请输入姓名：")
    password = input("请输入密码：")

    if username == "小二" and password == "123":
        print("登陆成功")
    else:
        if username != "小二":
            print("帐户名错误")
            print("你还有%d次机会" % (j))
            if i == 3:
                answer = input("再试试？")
                if answer == "y":
                    i = 0
        elif username == "小二":
            if password != "123":
                print("密码错误")
                print("你还有%d次机会" % (j))
                if i == 3:
                    answer = input("再试试？")
                    if answer == "y":
                        i = 0

 2、格式化输出

name = input('请输入姓名')
age = input('年龄')

msg = "我是%s,今年%s岁" %(name,age)

print(msg)

3、不包括88，求1-2+3-4...+99-100的和

i=0
sum = 0
while i<100 :
    i += 1
    if i == 88 :
        continue
    elif i % 2 == 0:
        sum -= i
    else:
        sum += i
print(sum)

i = 0
sum = 0
while i<100 :
    i += 1
    if i == 88 :
        continue
    elif i<88 :
        if i % 2 == 0:
            sum -= i
        else:
            sum += i
    else:
        if i % 2 == 0:
            sum += i
        else:
            sum -= i
print(sum)
print(i)