stack-queue.py

class stack:
   def __init__(self):
      self.storage=[]
      self.count=0

   def empty(self):
      if (self.count==0):
         return True
      else:
         return False

   def store(self,x):
      self.storage = self.storage + [x]
      self.count = self.count + 1
      return True

   def retrieve(self):
      if (self.count==0):
         return [False,0]
      else:
         self.count = self.count - 1
         rval = self.storage[-1]
         self.storage = self.storage[0:-1]
         return [True,rval]

class queue:
    def __init__(self):
        self.storage=[]
        self.cnt = 0

    def empty(self):
       if self.cnt==0:
          return True
       else:
          return False

    def store(self,value):
        self.storage=self.storage+[value]
        self.cnt = self.cnt + 1
        return self.cnt

    def retrieve(self):
        if (self.cnt==0):
            return [False,0]
        else:
            r=self.storage[0]
            self.cnt=self.cnt-1
            self.storage=self.storage[1:]
            return [True,r]