Using Stacks to Reverse Four Letters

This code can be used to add four letters to a stack and get them in reverse order

class Stack:
    def __init__(self):
        self.items = [] #create new list with no items

    def __repr__(self):
        return repr(self.items) #define what to return is the stackname is called

    def isEmpty(self):
        return self.items == [] #check whether list if empty and retuen T or F

    def size(self):
        return len(self.items) #return size of stack (= length of list)

    def push(self,val):
        self.items.append(val) #add the argument pass to the end of list

    def pop(self):
        return self.items.pop() #return the last item in list because index not specified

    def peek(self):
        return self.items[-1] #return last item (-1 because from right indices are negative)

#Create the stack
thestack=Stack()

thestack.push('A')  #add A to stack
thestack.push('B')  #add B to stack
thestack.push('C')  #add C to stack
thestack.push('D')  #add D to stack

print(thestack)

print (thestack.pop())  #pop the top item ie D
print (thestack.pop())  #pop the top item ie C
print (thestack.pop())  #pop the top item ie B
print (thestack.pop())  #pop the top item ie A

 


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