Implementation of a simple STACK

stack.py

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

    def push(self, item):
        self.arr.append(item)

    def pop(self):
        if self.arr:
            self.arr.pop()
        else:
            return 'Empty stack'

    def poll(self):
        if self.arr:
            return self.arr[-1]
        else:
            return 'Empty stack'

    def size(self):
        return len(self.arr)

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


s = Stack()
s.push(2)
s.push(3)
print(s)
s.pop()
print(s)
print([1, 2, 3, 4])