Valid Parentheses

class Solution(object):
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        dic={')':'(',']':'[','}':'{'}
        stack=[]
        for i in range(len(s)):
            if(s[i] in dic.values()):
                stack.append(s[i])
            else:
                if(len(stack)==0):
                    return False
                else:
                    if(dic[s[i]]!=stack[-1]):
                        return False
                    else:
                        stack.pop()
            
        return len(stack)==0