day04流程控制之while循环

流程控制之while循环

1、什么是while循环

　　　　　　循环指的是一个重复做某件事的过程

2、为何有循环

为了让计算机能像人一样重复 做某件事

3、如何用循环

 '''
 # while循环的语法:while循环又称为条件循环,循环的次数取决于条件
 '''
 while 条件:
     子代码1
     子代码2
     子代码3
 '''
 # print('start....')
 # while True:
 #     name=input('please your name>>: ')
 #     pwd=input('please your password>>: ')
 #     if name == 'egon' and pwd == '123':
 #         print('login successful')
 #     else:
 #         print('user or password err')
 # print('end...')

 # 如何结束while循环
 # 方式一:操作while循环的条件让其结束
 # print('start....')
 # tag=True
 # while tag:
 #     name=input('please your name>>: ')
 #     pwd=input('please your password>>: ')
 #     if name == 'egon' and pwd == '123':
 #         print('login successful')
 #         tag=False
 #     else:
 #         print('user or password err')
 #
 # print('end...')

 # 方式二: break强行终止本层循环
 # count=1
 # while count < 6:
 #     print(count)
 #     count+=1

 # count=1
 # while True:
 #     if count > 5:
 #         break
 #     print(count)
 #     count+=1

 # print('start....')
 # while True:
 #     name=input('please your name>>: ')
 #     pwd=input('please your password>>: ')
 #     if name == 'egon' and pwd == '123':
 #         print('login successful')
 #         break
 #     else:
 #         print('user or password err')
 #
 # print('end...')

 # 输错三次则退出
 # 方式一:
 # print('start....')
 # count=0
 # while count <= 2: #count=3
 #     name=input('please your name>>: ')
 #     pwd=input('please your password>>: ')
 #     if name == 'egon' and pwd == '123':
 #         print('login successful')
 #         break
 #     else:
 #         print('user or password err')
 #         count+=1
 #
 # print('end...')

 # 方式二
 # print('start....')
 # count=0
 # while True:
 #     if count == 3:
 #         print('输错的次数过多傻叉')
 #         break
 #     name=input('please your name>>: ')
 #     pwd=input('please your password>>: ')
 #     if name == 'egon' and pwd == '123':
 #         print('login successful')
 #         break
 #     else:
 #         print('user or password err')
 #         count+=1
 #
 # print('end...')

 # while+continue:continue代表结束本次循环,直接进入下一次
 # count=1
 # while count < 6:
 #     if count ==  4:
 #         count+=1
 #         continue # 只能在cotinue同一级别之前加代码
 #     print(count)
 #     count+=1
 #
 #
 # while True:
 #     print('11111')
 #     print('22222')
 #     print('333')
 #     continue # 不应该将continue作为循环体最后一步执行的代码

 # while+else
 # count=1
 # while count < 6:
 #     if count == 4:
 #         break
 #     print(count)
 #     count+=1
 # else:
 #     print('会在while循环没有被break终止的情况下执行')

 # 输错三次则退出之while+else的应用
 # print('start....')
 # count=0
 # while count <= 2: #count=3
 #     name=input('please your name>>: ')
 #     pwd=input('please your password>>: ')
 #     if name == 'egon' and pwd == '123':
 #         print('login successful')
 #         break
 #     else:
 #         print('user or password err')
 #         count+=1
 # else:
 #     print('输错的次数过多')
 #
 # print('end...')

 # while循环的嵌套
 # name_of_db='egon'
 # pwd_of_db='123'
 # print('start....')
 # count=0
 # while count <= 2: #count=3
 #     name=input('please your name>>: ')
 #     pwd=input('please your password>>: ')
 #     if name == name_of_db and pwd == pwd_of_db:
 #         print('login successful')
 #         while True:
 #             print("""
 #             1 浏览商品
 #             2 添加购物车
 #             3 支付
 #             4 退出
 #             """)
 #             choice=input('请输入你的操作: ') #choice='1'
 #             if choice == '1':
 #                 print('开始浏览商品....')
 #             elif choice == '2':
 #                 print('正在添加购物车....')
 #             elif choice == '3':
 #                 print('正在支付....')
 #             elif choice == '4':
 #                 break
 #         break
 #     else:
 #         print('user or password err')
 #         count+=1
 # else:
 #     print('输错的次数过多')
 #
 # print('end...')

 # tag控制所有while循环
 name_of_db='egon'
 pwd_of_db='123'
 tag=True
 print('start....')
 count=0
 while tag:
     if count == 3:
         print('尝试次数过多')
         break
     name=input('please your name>>: ')
     pwd=input('please your password>>: ')
     if name == name_of_db and pwd == pwd_of_db:
         print('login successful')
         while tag:
             print("""
             1 浏览商品
             2 添加购物车
             3 支付
             4 退出
             """)
             choice=input('请输入你的操作: ') #choice='1'
             if choice == '1':
                 print('开始浏览商品....')
             elif choice == '2':
                 print('正在添加购物车....')
             elif choice == '3':
                 print('正在支付....')
             elif choice == '4':
                 tag=False

     else:
         print('user or password err')
         count+=1

 print('end...')