balanced-delimiters.py

open_symbols = ['(', '{', '[']
close_symbols = [')', '}', ']']


def main():
    symbols = raw_input()

    opened_once = False
    open_list = []
    close_list = []

    last_open = False
    for symbol in list(symbols):
        # comment out this if, if you want to allow multiple open/close delimiters from the start
        if opened_once is True and not len(open_list):
            return False
        if symbol not in open_symbols and symbol not in close_symbols:
            return False

        if symbol in open_symbols:
            opened_once = True
            open_list.append(symbol)
            last_open = symbol
        elif symbol in close_symbols:
            close_list.append(symbol)

            open_match = close_symbols.index(symbol)
            if last_open == open_symbols[open_match]:
                open_list.pop(len(open_list)-1)
                close_list.pop(len(close_list)-1)
                if len(open_list):
                    last_open = open_list[-1]

    if len(open_list) > 0 or len(close_list) > 0:
        return False
    return True


print(main())