Study 7 —— while循环中止语句

循环的终止语句
break 　　 #用于完全结束一个循环，跳出循环体执行循环后面的语句
continue 　　 #只终止本次循环，接着执行后面的循环

1. 打印0-100，截止到第6次

count = 0
while count <= 100:
    print('Value: ', count)
　　if count == 5:
	　　break
　　count += 1

2. 打印0-100，截止到第6次，第6次无限循环打印

count = 0
while count <= 100:
    print('Value: ', count)
    if count == 5:
	　　continue
    count += 1

3. 打印1-5，95-101

count = 0
while count <= 100:
    count += 1
    if count > 5 and count < 95:
	　　continue
    print('Value: ', count)

4. 猜年龄，允许用户猜三次，中间猜对跳出循环

count = 0
age =18

while count < 3:
    user_guess = int(input('Input Number: '))
    if user_guess == age:
	　　print('Yes, you are right!')
	　　break
    elif user_guess > age:
	　　print('Try smaller!')
    else:
	　　print('Try bigger!')

    count += 1

5. 猜年龄，允许用户猜三次，中间猜对跳出循环，猜了三次后若没有猜对，询问是否继续，Y则继续，N则结束

count = 0
age =18

while count < 3:
    user_guess = int(input('Input Number: '))
    if user_guess == age:
	　　print('Yes, you are right!')
	　　break
    　　elif user_guess > age:
	　　　　print('Try smaller!')
    　　else:
	　　　　print('Try bigger!')
    　　count += 1

    if count == 3:
	　　choice = input('Whether or not to continue?(Y/N): ')
	　　if choice == 'Y' or choice == 'y':
	    　　count = 0
	　　elif choice == 'N' or choice == 'n':
	    　　pass
	　　else:
	    　　print('You must input Y/y or N/n !')
	    　　pass

6. 帐号密码判断

ACCOUNT = 'yancy'
PASSWD = '123!'

count = 0

while count < 1:
    account = input('Enter your account: ')
    passwd = input('Enter your password: ')

    if account == ACCOUNT and passwd == PASSWD:
        print('Welcome to the sso system!')
        break
    elif account == ACCOUNT and passwd != PASSWD:
        print('Your password is wrong!')
    elif account != ACCOUNT:
        print("Your account doesn't exist!")
    count += 1

    if count == 1:
        while True:
            choice = input('Whether not continue?(Y/N): ')
            if choice == 'Y' or choice == 'y':
                count = 0
                break
            elif choice == 'N' or choice == 'n':
                print('You quit the program!')
                break
            else:
                print("You must enter 'Y/y' or 'N/n'!")
                continue

while ... else语法

当while循环正常执行完毕，中间没有被break中止，就会执行else后面的语句

count = 0
while count <= 100:
    print('Value: ', count)
    if count == 5:
	　　break       #有break时，else下面的内容就不打印，没有break时，就打印。
    count += 1
else：
    print('loop is done.')

else语法可用于判断while程序中间是否被break中断跳出