class Solution:
    def isValid(self, s: str) -> bool:
        stack = []
        lib = {}
        lib[')'] = '('
        lib[']'] = '['
        lib['}'] = '{'
        for i in s:
            if i in lib: 
                if len(stack) == 0 or stack.pop() != lib[i]:
                    return False
            else:
                stack.append(i)
        if len(stack) == 0:
            return True
        return False