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...')