1. Stack using Python List

In [1]:

class Stack:
    def __init__(self):
        self.items = []
        self.__top = -1

    def is_empty(self):
        return self.__top == -1
        # return len(self.items) == 0
        # return self.items == []

    def peek(self):
        if self.is_empty():
            print("Stack is empty, nothing to peek()")
        else:
            print("<Element: %s>" % self.items[-1])

    def __repr__(self):
        items = []

        for i in range(len(self.items) - 1, 0, -1):
            if i == self.__top:
                items.append("[Top: %s]" % self.items[i])
            else:
                items.append("[%s]" % self.items[i])

        return ", ".join(items)

    def __iter__(self):
        for i in range(len(self.items) - 1, 0, -1):
            yield self.items[i]

    def __len__(self):
        return len(self.items)

    def push(self, data):
        print("Inserting: {} into the stack".format(data))
        self.items.append(data)
        self.__top += 1

    def pop(self):
        if self.is_empty():
            print("Stack is empty, nothing to pop()")
        else:
            data = self.items.pop()
            print("Removing: {} from top of the stack".format(data))
            self.__top -= 1

class Stack: def __init__(self): self.items = [] self.__top = -1 def is_empty(self): return self.__top == -1 # return len(self.items) == 0 # return self.items == [] def peek(self): if self.is_empty(): print("Stack is empty, nothing to peek()") else: print("" % self.items[-1]) def __repr__(self): items = [] for i in range(len(self.items) - 1, 0, -1): if i == self.__top: items.append("[Top: %s]" % self.items[i]) else: items.append("[%s]" % self.items[i]) return ", ".join(items) def __iter__(self): for i in range(len(self.items) - 1, 0, -1): yield self.items[i] def __len__(self): return len(self.items) def push(self, data): print("Inserting: {} into the stack".format(data)) self.items.append(data) self.__top += 1 def pop(self): if self.is_empty(): print("Stack is empty, nothing to pop()") else: data = self.items.pop() print("Removing: {} from top of the stack".format(data)) self.__top -= 1

In [2]:

stack = Stack()

stack = Stack()

In [3]:

for i in range(0, 6):
    stack.push(i)

for i in range(0, 6): stack.push(i)

Inserting: 0 into the stack
Inserting: 1 into the stack
Inserting: 2 into the stack
Inserting: 3 into the stack
Inserting: 4 into the stack
Inserting: 5 into the stack

In [4]:

stack.pop()

stack.pop()

Removing: 5 from top of the stack

In [5]:

stack.is_empty()

stack.is_empty()

Out[5]:

False

In [6]:

stack.peek()

stack.peek()

<Element: 4>

In [7]:

stack

stack

Out[7]:

[Top: 4], [3], [2], [1]

In [8]:

for i in stack:
    print(i)

for i in stack: print(i)

4
3
2
1

In [9]:

len(stack)

len(stack)

Out[9]:

5

In [10]:

for _ in range(10):
    stack.pop()

for _ in range(10): stack.pop()

Removing: 4 from top of the stack
Removing: 3 from top of the stack
Removing: 2 from top of the stack
Removing: 1 from top of the stack
Removing: 0 from top of the stack
Stack is empty, nothing to pop()
Stack is empty, nothing to pop()
Stack is empty, nothing to pop()
Stack is empty, nothing to pop()
Stack is empty, nothing to pop()

In [ ]: