#!/usr/bin/python3

 # coding=utf-8

 # 实现switch-case语句

 class switch(object):

     def __init__(self, value):

         self.value = value

         self.fall = False

     def __iter__(self):

         """Return the match method once, then stop"""

         yield self.match

         raise StopIteration

     def match(self, *args):

         """Indicate whether or not to enter a case suite"""

         if self.fall or not args:

             return True

         elif self.value in args:  # changed for v1.5, see below

             self.fall = True

             return True

         else:

             return False

 class student:

     def __init__(self, name, age, id, grade):

         self.next = None

         self.name = name

         self.age = age

         self.id = id

         self.grade = grade

     def show(self):

         print('name:', self.name, ' ', 'age:', self.age, ' ', 'id:', self.id, ' ', 'grade:', self.grade)

 class stulist:

     def __init__(self):

         self.head = student('', 0, 0, 0)

     def display(self):

         p = self.head.next

         if p==None:

             print('no student data in database!')

         while p:

             p.show()

             p = p.next

     def insert(self):

         print('please enter:')

         name = input('name:')

         age = input('age:')

         id = input('id:')

         grade = input('grade:')

         newstu = student(name, age, id, grade)

         p = self.head

         while p.next:

             p = p.next

         p.next = newstu

     def query(self):

         name = input('please enter the name you want to query:')

         p = self.head.next

         if p==None:

             print('no such student in database')

         while p:

             if p.name == name:

                 p.show()

             p = p.next

     def delete(self):

         name = input("please enter the student'name you want to delete:")

         p = self.head.next

         pre = self.head

         while p:

             if p.name == name:

                 pre.next = p.next

                 p.next = None

                 print('the student info has been deleted!')

                 break

             else:

                 pre = p

                 p = p.next

 def main():

     stulist1 = stulist()

     user_input = input('please enter the OPcode:')

     while user_input:

         print('a--insert/b--display/c--query/h or ''--help/d--delete')

         for case in switch(user_input):

             if case('a'):

                 stulist1.insert()

                 user_input = input('please enter the OPcode:')

                 break

             if case('b'):

                 stulist1.display()

                 user_input = input('please enter the OPcode:')

                 break

             if case('c'):

                 stulist1.query()

                 user_input = input('please enter the OPcode:')

                 break

             if case('d'):

                 stulist1.delete()

                 user_input = input('please enter your OPcode:')

                 break

             if case():  # default

                 print('please enter the OPcode...')

                 user_input = input('please enter the OPcode:')

                 break

 if __name__ == "__main__":

     main()