Stack

class StackException(ValueError):
    pass


class Stack:
    stack_list = []

    def __init__(self, stack_type):
        self.stack_list = list()
        self.stack_type = stack_type

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

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

    def push(self, value):
        if not type(value) is self.stack_type and not issubclass(type(value), self.stack_type):
            raise StackException('Type Error: ', value)
        self.stack_list.append(value)
        print(self.stack_list)
        print('len:', len(self))

    def pop(self):
        if len(self.stack_list) == 0:
            raise StackException('Pop from empty stack')
        res = self.stack_list[-1]
        self.stack_list = self.stack_list[:len(self.stack_list) - 1]
        print(self.stack_list)
        print('len:', len(self))
        return res

    def clear(self):
        self.stack_list = list()
        print(self.stack_list)
        print(len(self))

    def is_empty(self):
        return True if len(self.stack_list) == 0 else False