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