finite_stacks.py

class Stack:

    def __init__(self, n):
        self.size = n
        self.data = [None] * n
        self.top = -1

    def push(self, e):
        if self.top + 1 == self.size:
            raise Exception('Stack overflowed')
        self.top += 1
        self.data[self.top] = e

    def pop(self):
        if self.top == -1:
            raise Exception('Stack underflowed')
        e = self.data[self.top]
        self.top -= 1
        return e