Leetcode: Valid Parentheses (Python)

valid_parentheses.py

    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        if len(s) % 2 != 0:
            return False

        par_dict = {'(':')','{':'}','[':']'}
        stack = []
        
        for char in s:
            if char in par_dict.keys():
                stack.append(char)
            else:
                if stack == []:
                    return False
                open_brac = stack.pop()
                if char != par_dict[open_brac]:
                    return False

        return stack == []