Lesson 9, Python 3

Lesson 9

# Object Oriented Programming - Data Structure Stack

'''
    Stack - LIFO (Last In First Out)
    
    1. Extracting book 4
    Book 1 --->>
    Book 2 --->>
    Book 3 --->>
    Book 4           Book 4
    Book 5           Book 5
    Book 6           Book 6
    
    
    2. Removing from pile of books (always the thing on top) (Popping)
    
    Book 4 --->>
    Book 3
    Book 2
    Book 1

3. Adding Book 5 to the pile (always on the top) (Pushing)

Book 5
    Book 4
    Book 3
    Book 2
    Book 1

'''

class Stack:
    def __init__(self):
        self.items = []   # empty list
        
    def push(self, add_an_item):
        return self.items.append(add_an_item)
    
    def pop(self):
        if self.isEmpty() is True:
            return []
        else:  # stack not empty
            return self.items.pop()
    
    def show(self):
        print (self.items[:])
    
    def isEmpty(self):
        if self.items == []:
            return True
        else:
            return False
    
    def size(self):
        return len(self.items)
    
stack_1 = Stack()
stack_1.push('Pillow')
stack_1.push('Brush')

stack_1.push('Mattress')
stack_1.push('Bags')
stack_1.push('Car')
stack_1.pop()
stack_1.push('Pillow')
stack_1.push('Brush')
stack_1.push('Mattress')
stack_1.push('Bags')
stack_1.push('Car')
print (stack_1.size())

stack_1.pop()

stack_1.pop()
stack_1.show()


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