Leetcode: Count and Say @Python

class Solution:
    # @return a string
    def itergen(self,a):
        k,last,result = 1,a[0],''
        for i in range(1,len(a)):
            if last==a[i]:k+=1
            else:
                result = result+str(k)+last
                k=1
                last = a[i]
        result = result+str(k)+last
        return result
    def countAndSay(self, n):
        if n==0: return ''
        rst='1'
        for i in range(n-1):
            rst=self.itergen(rst)
        return rst