Leetcode 38 Count and Say

class Solution(object):
    def countAndSay(self, n):
        """
        :type n: int
        :rtype: str
        """
        if n==1:
            return ‘1‘
        else:
            sequence = self.countAndSay(n-1)
            left,right,num,size=0,0,0,len(sequence)
            ans=‘‘
            while right<=size:
                if right == size:
                    ans+=str(num)+sequence[left]
                    break
                if sequence[right]==sequence[left]:
                    num+=1
                    right+=1
                else:
                    ans+=str(num)+sequence[left]
                    left=right
                    num=0
        return ans