流程控制值while 循环

一.结束循环的两种方式
  1. 修改条件
tag=True
while tag:
    print(1)
    print(2)
    print(3)
    tag=False
    print(4)
  2.while + break 直接结束本次循环
while True:
    while True:
        while True:
            break
        break
    break

案列一:特点是在输错三次后还可以打印 提示输入次数过多
name='deng'
pwd='123'
count=0
while True:
    name_inp=input('please input your name:')
    pwd_inp=input('please input your password:')
    if name_inp == name and pwd_inp ==pwd:
        print('login successful')
        break
    else:
        print('user or password error')
        count+=1
    if count ==3:
        print('too many error')
        break

案列二:特点是在输错三次后直接结束循环
name='deng'
pwd='123'
count=0
while count < 3:
    name_inp = input('please input your name:')
    pwd_inp=input('please input your password:')
    if name_inp == name and pwd_inp == pwd:
        print('login successsful')
        break
    else:
        print('user or password error')
        count+=1

二. while + continue
continue 代表结束本次循环,直接进入下一次循环
案列一:0到10之间所有的数字,除了5,其余的分别打印出来
n=0
while n < 10:
    if n == 5:
        n+=1
        continue
    print(n)
    n+=1

 不合理示范1
while True:
    print(1)
    print(2)
    print(3)
    continue

不合理示范2
while True:
    print(1)
    print(2)
    if 1 == 2:
        pass
    else:
        print('xxxx')
        continue

三.while嵌套
案列一
name='deng'
pwd='123'
count=0
while True:
    name_inp=input('please input your name:')
    pwd_inp=input('please input your password:')
    if name_inp == name and pwd_inp == pwd:
        print('login successful')
        while True:
            print('''
                 0 退出
                 1 取款
                 2 转账
                 3 查询
            ''')
            cmd = input('请输入指令编号:')
            if cmd == '0':
                break
            elif cmd == '1':
                print('取款')
            elif cmd == '2':
                print('转账')
            elif cmd == '3':
                print('查询')
            else:
                print('输入的指令错误,请重新输入!!!')
        break
    else:
        print('user or password error')
        count+=1
    if count == 3:
        print('输错次数过多!!!')
        break

案例二：
name='egon'
pwd='123'
count=0
tag=True
while tag:
    inp_name=input('please input your name: ')
    inp_pwd=input('please input your password: ')
    if inp_name == name and inp_pwd == pwd:
        print('login successful')

        while tag:
            print("""
                   0 退出
                   1 取款
                   2 转账
                   3 查询
                   """)
            cmd = input('请输入指令编号>>>: ')  # cmd='0'
            if cmd == '0':
                tag=False
            elif cmd == '1':
                print('取款...')
            elif cmd == '2':
                print('转账...')
            elif cmd == '3':
                print('查询...')
            else:
                print("输入错误指令，请重新输入")

    else:
        print('user or passwor error')
        count+=1 #count=3

    if count == 3:
        print('too many tries.....')
        break
三：while+else
else:如果while循环没有被break打断过，即正常运行完毕后才会执行else的子代码块
n=0
while True:
    # if n == 3:
    #     break
    print(n)
    n+=1
else:
    print('run.....')

n=0
while n <= 3:
    print(n)
    n+=1
else:
    print('run.....')