[python] Stacks and Queues > Balanced Brackets

#!/bin/python3

import math
import os
import random
import re
import sys


def isBalanced(s):
    stack = []
    for char in s:
        if char in ['{','[','(']:
            stack.append(char)
        else:
            try:
                x = stack.pop()
                if char == '}' and x != '{':
                    return 'NO'
                elif char == ']' and x != '[':
                    return 'NO'
                elif char == ')' and x != '(':
                    return 'NO'
                else:
                    pass
            except IndexError:
                return 'NO'
    if len(stack) == 0:
        return 'YES'
    else:
        return 'NO'