Leetcode 219 Contains Duplicate II

class Solution:
    # @param {integer[]} nums
    # @param {integer} k
    # @return {boolean}
    def containsNearbyDuplicate(self, nums, k):
        dictNums = {}
        for i in range(len(nums)):
            index = dictNums.get(nums[i])
            if (index >= 0 and i-index <= k):
                return True
            dictNums[nums[i]] = i
        return False