Implement a Basic Stack (LIFO) with Python Lists

class Stack:
    def __init__(self):
        self._items = []

    def push(self, item):
        """Adds an item to the top of the stack."""
        self._items.append(item)

    def pop(self):
        """Removes and returns the item from the top of the stack.
        Raises an IndexError if the stack is empty."""
        if not self.is_empty():
            return self._items.pop()
        raise IndexError("pop from empty stack")

    def peek(self):
        """Returns the item at the top of the stack without removing it.
        Raises an IndexError if the stack is empty."""
        if not self.is_empty():
            return self._items[-1]
        raise IndexError("peek from empty stack")

    def is_empty(self):
        """Checks if the stack is empty."""
        return len(self._items) == 0

    def size(self):
        """Returns the number of items in the stack."""
        return len(self._items)

    def __str__(self):
        return str(self._items)

# Example Usage:
my_stack = Stack()
print(f"Is stack empty? {my_stack.is_empty()}") # True

my_stack.push(10)
my_stack.push(20)
my_stack.push(30)
print(f"Stack after pushes: {my_stack}") # [10, 20, 30]
print(f"Stack size: {my_stack.size()}") # 3

print(f"Top element (peek): {my_stack.peek()}") # 30
print(f"Popped element: {my_stack.pop()}") # 30
print(f"Stack after pop: {my_stack}") # [10, 20]

print(f"Popped element: {my_stack.pop()}") # 20
print(f"Stack after pop: {my_stack}") # [10]

print(f"Is stack empty? {my_stack.is_empty()}") # False