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流程控制之while循环

# 1、循环的语法与基本使用
'''
print(1)
while 条件:
代码1
代码2
代码3
print(3)
'''

# count=0
# while count < 5: # 5 < 5
# print(count) # 0,1,2,3,4
# count+=1 # 5
#
# print('顶级代码----->')


# 2、死循环与效率问题
# count=0
# while count < 5: # 5 < 5
# print(count) # 0,1,2,3,4

# while True:
# name=input('your name >>>> ')
# print(name)

# 纯计算无io的死循环会导致致命的效率问题
# while True:
# 1+1

# while 1:
# print('xxxx')

# 3、循环的应用
username = 'egon'
password = '123'

# 两个问题:
# 1、重复代码
# 2、输对了应该不用再重复
# while True:
# inp_name=input('请输入您的账号:')
# inp_pwd=input('请输入您的密码:')
#
# if inp_name == username and inp_pwd == password:
# print('登录成功')
# else:
# print('账号名或密码错误')


# 4、退出循环的两种方式
# 方式一:将条件改为False,等到下次循环判断条件时才会生效
# tag=True
# while tag:
# inp_name=input('请输入您的账号:')
# inp_pwd=input('请输入您的密码:')
#
# if inp_name == username and inp_pwd == password:
# print('登录成功')
# tag = False # 之后的代码还会运行,下次循环判断条件时才生效
# else:
# print('账号名或密码错误')
#
# # print('====end====')

# 方式二:break,只要运行到break就会立刻终止本层循环
# while True:
# inp_name=input('请输入您的账号:')
# inp_pwd=input('请输入您的密码:')
#
# if inp_name == username and inp_pwd == password:
# print('登录成功')
# break # 立刻终止本层循环
# else:
# print('账号名或密码错误')
#
# # print('====end====')


# 7、while循环嵌套与结束
'''
tag=True
while tag:
while tag:
while tag:
tag=False


# 每一层都必须配一个break
while True:
while True:
while True:
break
break
break
'''
## break的方式
# while True:
# inp_name=input('请输入您的账号:')
# inp_pwd=input('请输入您的密码:')
#
# if inp_name == username and inp_pwd == password:
# print('登录成功')
# while True:
# cmd=input("输入命令>: ")
# if cmd == 'q':
# break
# print('命令{x}正在运行'.format(x=cmd))
# break # 立刻终止本层循环
# else:
# print('账号名或密码错误')
#
# # print('====end====')

# # 改变条件的方式
# tag=True
# while tag:
# inp_name=input('请输入您的账号:')
# inp_pwd=input('请输入您的密码:')
#
# if inp_name == username and inp_pwd == password:
# print('登录成功')
# while tag:
# cmd=input("输入命令>: ")
# if cmd == 'q':
# tag=False
# else:
# print('命令{x}正在运行'.format(x=cmd))
# else:
# print('账号名或密码错误')


# 8、while +continue:结束本次循环,直接进入下一次
# 强调:在continue之后添加同级代码毫无意义,因为永远无法运行
# count=0
# while count < 6:
# if count == 4:
# count+=1
# continue
# # count+=1 # 错误
# print(count)
# count+=1

# 9、while +else:针对break
# count=0
# while count < 6:
# if count == 4:
# count+=1
# continue
# print(count)
# count+=1
# else:
# print('else包含的代码会在while循环结束后,并且while循环是在没有被break打断的情况下正常结束的,才会运行')

# count=0
# while count < 6:
# if count == 4:
# break
# print(count)
# count+=1
# else:
# print('======>')


# 应用案列:
# 版本1:
# count=0
# tag=True
# while tag:
# if count == 3:
# print('输错三次退出')
# break
# inp_name=input('请输入您的账号:')
# inp_pwd=input('请输入您的密码:')
#
# if inp_name == username and inp_pwd == password:
# print('登录成功')
# while tag:
# cmd=input("输入命令>: ")
# if cmd == 'q':
# tag=False
# else:
# print('命令{x}正在运行'.format(x=cmd))
# else:
# print('账号名或密码错误')
# count+=1

# 版本2:优化
count = 0
while count < 3:
inp_name = input('请输入您的账号:')
inp_pwd = input('请输入您的密码:')

if inp_name == username and inp_pwd == password:
print('登录成功')
while True:
cmd = input("输入命令>: ")
if cmd == 'q': # 整个程序结束,退出所有while循环
break
else:
print('命令{x}正在运行'.format(x=cmd))
break
else:
print('账号名或密码错误')
count += 1
else:
print('输错3次,退出')
posted @ 2020-03-09 15:17  臭弟弟d  阅读(221)  评论(0编辑  收藏  举报