Parse JSONIsh brackets

parse.py

class Solution:
    openers = ["(", "{", "["]
    closers = [")", "}", "]"]
    valid = openers + closers

    def __init__(self):
        self.stack = []

    def push(self, x):
        self.stack.append(x)

    def pop(self):
        if len(self.stack) > 0:
            return self.stack.pop()

    def isValid(self, s: str) -> bool:
        if len(s) < 2:
            return False

        for c in s:
            if c not in self.__class__.valid:
                raise ValueError("Invalid character: '{c}'. Valid characters: '{valid}'.")
            if c in self.__class__.openers:
                self.push(c)
            elif c in self.__class__.closers and (len(self.stack) == 0):
                return False
            else:  # is closer
                o = self.pop()
                if c and o and (self.__class__.openers.index(o) != self.__class__.closers.index(c)):
                    print("Invalid character: '{c}' does not match '{o}'.")
                    return False
        if len(self.stack) > 0:
            return False
        return True