Solution.py

class Solution:
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        a="()"
        b="[]"
        c="{}"
        f=False
        if s == '':
            return True
        while s != '':
            s=s.replace(a,'')
            s=s.replace(b,'')
            s=s.replace(c,'')
            if s == '':
                f=True
                return f
            if (a in s) or (b in s) or (c in s):
                pass
            else:
                f=False
                return f

class Solution():
    def isValid(self,s):
        """
        :type s: str
        :rtype: bool
        """
        left=['(','{','[']
        right={ ')':'(',
                ']':'[',
                '}':'{' }
        stack=[]
        for i in s:
            if i in left:
                stack.append(i)
            elif stack and right[i] == stack.pop():
                continue
            else:
                return False
        if stack:
            return False
        return True