stack_challenge_solution.py

class Stack:

    def __init__(self):
        self.items = []

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

    def pop(self):
        if self.items:
            return self.items.pop()

        return None
        
    def is_empty(self):
        return self.items == []


def match_symbols(symbol_str):

    symbol_pairs = {
        '(':')',
        '[':']',
        '{':'}',
        }

    openers = symbol_pairs.keys()
    my_stack = Stack()

    index = 0
    while index < len(symbol_str):
        symbol = symbol_str[index]

        if symbol in openers:
            my_stack.push(symbol)

        else: # The symbol is a closer

            # If the Stack is already empty, the symbols are not balanced
            if my_stack.is_empty():
                return False

            # If there are still items in the Stack, check for a mis-match.
            else:
                top_item = my_stack.pop()
                if symbol != symbol_pairs[top_item]:
                    return False

        index += 1

    if my_stack.is_empty():
        return True

    return False # Stack is not empty so symbols were not balanced

print(match_symbols('([{}])'))
print(match_symbols('(([{}]])]'))