dynamic_stack.py

# Stack: Last In - First Out (LIFO)


# Define node format: value and a pointier to next
class Node:
    def __init__(self, value: int) -> None:
        self.value = value
        self.next = None


class DynamicStack:
    def __init__(self) -> None:
        self.__first = None

    def isEmpty(self) -> bool:
        if not self.__first:
            return True
        return False

    def push(self, value: int):
        node = Node(value)
        node.next = self.__first
        self.__first = node

    def pop(self) -> int:
        if self.isEmpty():
            raise Exception("Stack is empty!")
        removedElement = self.__first.value
        self.__first = self.__first.next
        return removedElement

    def show(self) -> None:
        node = self.__first
        print("[", end=" ")
        while node:
            print(node.value, end=" ")
            node = node.next
        print("]")


def main() -> None:
    dynamic_stack = DynamicStack()

    print("Push(1,2,4):")
    dynamic_stack.push(1)
    dynamic_stack.push(2)
    dynamic_stack.push(4)

    dynamic_stack.show()

    print(f"Remove last: {dynamic_stack.pop()}")
    print(f"Remove last: {dynamic_stack.pop()}")
    print(f"Remove last: {dynamic_stack.pop()}")
    print("Empty stack!")
    dynamic_stack.show()


if __name__ == "__main__":
    main()