python入门练习题

1、使用while循环输入 1 2 3 4 5 6     8 9 10

num = 1
while num<=10:
    if num ==7:
        num += 1
        continue
    print(num)
    num += 1

2、求1-100的所有数的和

num = 1
sum = 0
while num<=100:
    sum += num
    num += 1
print(sum)

3、输出 1-100 内的所有奇数

num = 1
while num<=100:
    if num%2 ==0:
        num += 1
        continue
    print(num)
    num +=1

4、求1-2+3-4+5 ... 99的所有数的和

num = 1
sum = 0
while num<=100:
    if num%2 ==0:
        sum += num
    else:
        sum -= num
    num +=1
print(sum)

5.用户登陆（三次机会重试）

count = 0
while True:
    usrname = input("usrname>>>")
    password = input("password>>>")
    ":
        print("enter ok")
        break
    else:
        print("usrname or password false,please again")
        count +=1
        if count==3:
            print("3 times over,you are false")
            break
        continue