流程控制之while循环
1.什么是循环
循环就是重复做某件事
2.为什么要有循环
为了让计算机能够具备人重复做某件事的能力
3.如何用循环
while语法：
while 条件：
code1
code2
code3
结束while循环的两种方式：
1.修改条件：等到下一次循环开始时判断条件为假才会结束while循环
2.break：直接结束本层循环
tag=False 到下次判断才会结束
break 直接结束
# count =0
# while count<3:
# inp_name =input('your name:')
# inp_pwd = input('your pwd:')
# if inp_name == 'egon'and inp_pwd=='123':
# print('success!')
# break
# else:
# print('name or pwd error!')
# count+=1
# count =0
# while True:
# inp_name = input('your name:')
# inp_pwd =input('uor pwd:')
# if inp_name =='egon'and inp_pwd=='123':
# print('success!')
# break
# else:
# print('name or pwd error!')
# count+=1
# if count ==3:
# print('too many tries...')
# break
一：while+continue
continue:结束本次循环，直接进入下一次循环
# 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
# 案例一：
# n=0
# while n < 6: #n=6
# if n == 4:
# n+=1
# continue
# print(n)
# n+=1
二：while循环嵌套
# 案例一：
#name='egon'
#pwd='123'
#count=0
# while True:
# 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 True:
# 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':
# break
# 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")
# break
# else:
# print('user or password error')
# count+=1 #count=3
#
# if count == 3:
# print('too many tries.....')
# 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 password error')
# count+=1 #count=3
#
# if count == 3:
# print('too many tries.....')
# break
# count =True
# while count:
# inp_name= input('your name:')
# inp_pwd = input('your pwd:')
# if inp_name =='egon' and inp_pwd=='123':
# print('success!')
# while count:
# 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':
# count=False
# elif cmd=='1':
# print('取款。。')
# elif cmd=='2':
# print('转账。。。')
# elif cmd =='3':
# print('查询')
# else:
# print('请输入指定的指令编号：')
#
# else:
# print('your name or pwd error')
# count +=1
# 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
# 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..')
#
# n= 0
# while n<=3:
# print(n)
# n+=1
# else:
# print('run,,')
for 循环 在循环取值方面比while循环更为简洁
# lis =[1,2,3,4,5,6]
# i = 0
# while i<len(lis):
# print(lis[i])
# i+=1
# dic={'name':'egon','age':18,'sex':'male'}
# for k in dic:
# print(k,dic[k])
# for+break
# for+continue
# for+else
# lis =[1,2,3,4,5,6]
# for i in lis:
# print(i)
# dic = {'name':'egon','age':18,'sex':'male'}
# for item in dic:
# print(item,dic[item])
#
# dic = {'name':'egon','age':18,'sex':'male'}
# for k in dic:
# # if k =='age':break
# print(k,dic[k])
# else:
# print('run..')
# dic ={'name':'egon','age':18,'sex':'male'}
# for k in dic :
# print(k,dic[k])
# else:
# print('run..')
# for i in range(1,5,2):
# print(i)
可变不可变类型
可变类型：值改变，但是ID不变，证明是改变原值
不可变类型：值改变，id也变，证明是产生了新之，没有改变原值，例如整型