Leetcode 202 Happy Number

class Solution:
    # @param {integer} n
    # @return {boolean}
    def isHappy(self, n):
        squart = dict([(i, int(i)**2) for i in '0123456789'])
        numSet = set()
        while n != 1 and n not in numSet:
            numSet.add(n)
            n = sum(squart[d] for d in str(n))
        return n == 1