DVD management system

• #usr/bin/python
  #-*-coding:utf-8-*-
  '''
  ----DVD Management System----:
  1. Query all DVDs
  2. Add DVD
  3. Lending DVDs
  4. Return the DVD
  5. Exit
  '''
  class dvd:
  
      def __init__(self,name,price,state):
          self.name=name;
          self.price=price
          self.state=state
  
      def __str__(self):
          stat='Loaned';
          if self.state==1:
              stat='Not loaned'
          return 'Name: "%s" Unit price: %d Status: %s'%(self.name,self.price,stat)
  
  class DVDManager:
      #Store multiple dvds Each element is a DVD
      dvds=[]
      def init(self):
          self.dvds.append(dvd('Glorious Years',10,0));
          self.dvds.append(dvd('Gentleman', 5, 1));
          self.dvds.append(dvd('Broad seas and sky', 11, 1));
  
      def Menu(self):
          self.init()
          while(True):
              print('1. Query all DVDs')
              print('2. Add DVD')
              print('3. Lend DVD')
              print('4. Return DVD')
              print('5. Exit')
              choose=int(input('Please choose:'));
              if choose==1:
                  self.showAllDVD();
              elif choose==2:
                  self.insertDVD();
              elif choose==3:
                  self.jiechuDVD();
              elif choose==4:
                  self.rollBackDVD();
              elif choose==5:
                  print('5. Thank you for using')
                  break;
  
      def showAllDVD(self):
          for d in self.dvds:
              print(str(d))
      def jiechuDVD(self):
          name = input('Please enter the name of the DVD:')
          ret = self.checkDVD(name);
          if ret != None:
              if ret.state==0:
                  print('dvd has been lent out')
                  #return;
              else:
                  days=int(input('Please enter the loan days:'))
                  ret.state = 0;
                  print('Lending %d days, interest %d '%(days,ret.price*days))
  
          else:
              print('DVD does not exist!')
  
      def rollBackDVD(self):
          name = input('Please enter the name of the returned DVD:')
          ret = self.checkDVD(name);
          if ret == None:
              print('DVD does not exist!')
          else:
              if ret.state == 1:
                  print('dvd not loaned!')
              else:
                  days= int(input('Please enter how many days have you borrowed?'))
                  y_money=ret.price * days
                  print('loan %d days, interest %d ' % (days, y_money))
                  money= int(input());
                  if money<y_money:
                      print('Not enough!')
                      return;
                  elif money>y_money:
                      print('Change: %d'%(money-y_money));
  
                  ret.state = 1;
                  print('Successful return!')
  
      def insertDVD(self):
          name = input('Please enter the name of the DVD:')
          ret= self.checkDVD(name);
          if ret != None:
              print('DVD already exists!')
          else:
              price=int(input('Please enter the price:'))
              new_dvd=dvd(name,price,1);
              self.dvds.append(new_dvd)
              print('Save successfully!')
      def checkDVD(self,name):
           for d in self.dvds:
               if d.name==name:
                   return d;#return the current object --> memory address
           else:
               return  None;
  
  manager= DVDManager();
  manager.Menu();