python day04

一.常量

在python中没有一个专门的语法代表常量程序员约定俗称用变量名的全部大写代表常量

二.基本运算符补充

1.算术运算

print(10 / 3)

print(10 // 3

2.赋值运算之增量赋值

例 age=18

age=age+1

age += 1

3.赋值预算之交叉赋值

例 x=10 y=20

temp=x

y=x

temp=y

x,y=y,x

4. 链式赋值

x=10

y=x

z=y
x=y=z=10
print(id(x))
print(id(y))
print(id(z))

5. 解压赋值

例:L[1.2,2.2,3.3,4.4,5.5]

a,b,c,d,e,=L

print(a,b,c,d,e)

三.if 判断

语法1

age_of_bk=30
 print('start...')

 inp_age=input('>>>:')
 inp_age=int(inp_age)
 if inp_age == age_of_bk:
     print('猜对了')
语法2

age=19
 gender='female'
 is_beautifui=True

 if age >= 18 and age <= 25 and gender == 'female' and is_beautifui:
     print('开始表白...')

 else:
     print('阿姨好')
语法3

 score=input('youe csore')
 score=int(score)
 if score >= 90:
     print('优秀')
 elif score >= 80:
     print('良好')
 elif score >= 70:
    print('普通')
 else:
     print('垃圾')

　　语法4

 age=50
 gender='famale'
 is_beautiful=True
 is_successful=True
 if age >=18 and age <= 25 and gender == 'famale' and is_beautiful:
     print('表白.....')
 else:
     print('我逗你玩呢')

四.while循环: 条件循环

 while之"条件循环"
 name_of_bk='egon'
 pwd_of_bk='123'
 tag=True
 while tag:
     inp_name=input('your name>>:')
     inp_pwd=input('your password>>:')
     if inp_name == name_of_bk and inp_pwd == pwd_of_bk:
         print('login successful')
         tag=False
     else:
         print('username or password error')
         print('other code...')

 while+break break代表结束本层循环
 while True:
     print(1)
     break
     print(2)
     print(3)
 name_of_bk='egon'
 pwd_of_bk='123'
 while True:
     inp_name=input('your name>>:')
     inp_pwd=input('your password>>:')
     if inp_name == name_of_bk and inp_pwd == pwd_of_bk:
         print('login successful')
         break
     else:
         print('urername or password error')
         print('other code...')

 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==3:         count+=1         continue     print(count)     count+=1 name_of_bk='egon' pwd_of_bk='123' count=0
 while True:
     if count == 3:

         print('输错的次数过多...')
         break
     inp_name=input('your name>>:')
     inp_pwd=input('your password>>:')
     if inp_name == name_of_bk and inp_pwd == pwd_of_bk:
         print('login successful')
         break
     else:
         print('username or password error')
         count += 1

 while+else else('else的子代码块只有在while循环没有被break打断的情况下才会执行')
 count = 0
 while True:
     if count == 10:
         break
     print(count)
     count += 1

 while+else else('else的子代码块只有在while循环没有被break打断的情况下才会执行')
 count = 0
 while True:
     if count == 10:
         break
     print(count)
     count += 1

 count=0
 while count <= 10:
     print(count)
     count += 1


 name_of_bk='egon'
 pwd_of_bk='123'

 count = 0
 tag = True
 while tag:
     if count == 3:
         print('输错的次数过多')
         break
     inp_name=input('your name>>:')
     inp_pwd=input('your password')
     if inp_name == name_of_bk and inp_pwd == pwd_of_bk:
         print('iogin successful')
         while tag:
             print("""
             0 退出
             1 购物
             2 支付
             3 查看购物
             """)
             cmd = input('>>>:')
             if cmd == '0':
                 tag = False
                 continue
             elif cmd == '1':
                 print('购物...')
             elif cmd == '2':
                 print('支付.....')
             elif cmd == '3':
                 print('查看购物车')
             else:
                 print('输入错误的指令')
     else:
         print('username or password error')
         count += 1

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