stack queue python code example

Example: python list as stack and queue

def isEmpty(stk): # checks whether the stack is empty or not
   if stk==[]:
      return True
   else:
      return False

def Push(stk,item): # Allow additions to the stack
   stk.append(item)
   top=len(stk)-1

def Pop(stk):
   if isEmpty(stk): # verifies whether the stack is empty or not
      print("Underflow")
   else: # Allow deletions from the stack
      item=stk.pop()
      if len(stk)==0:
         top=None
      else:
         top=len(stk)
         print("Popped item is "+str(item))

def Display(stk):
   if isEmpty(stk):
      print("Stack is empty")
   else:
      top=len(stk)-1
      print("Elements in the stack are: ")
      for i in range(top,-1,-1):
         print (str(stk[i]))

# executable code
if __name__ == "__main__":
   stk=[]
   top=None
   Push(stk,1)
   Push(stk,2)
   Push(stk,3)
   Push(stk,4)
   Pop(stk)
   Display(stk)