leetcode Combination Sum python

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:
All numbers (including target) will be positive integers.
Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
The solution set must not contain duplicate combinations.
For example, given candidate set 2,3,6,7 and target 7,
A solution set is:
[7]
[2, 2, 3] 

class Solution(object):
    def combinationSum(self, candidates, target):
        """
        :type candidates: List[int]
        :type target: int
        :rtype: List[List[int]]
        """
        candidates.sort()
        self.ret=[]

        self.dfs(candidates,target,0,[])
        return self.ret
    def dfs(self,candidates,target,start,valuelist):
        intlen=len(candidates)
        if target==0:
            return self.ret.append(valuelist)
        for i in range(start,intlen):
            if target < candidates[i]:
                return
            self.dfs(candidates,target-candidates[i],i,valuelist+[candidates[i]])