subsettt.py

class Solution:
    def subsets(self, nums):
        if not nums: return []
        self.res = []
        self.dfs(nums, [], 0)
        return self.res
    
    
    def dfs(self, nums, temp, index):
        if index == len(nums):
            self.res.append(temp[:])
            return

        # Case 1: Add number into temp array
        temp.append(nums[index])        
        self.dfs(nums, temp, index + 1)
        temp.pop()

        # Case 2: Add Nothing
        self.dfs(nums, temp, index + 1)



class Solution(object):
    def subsets(self, nums):
        if not nums: return []        
        self.res = []
        self.dfs(nums, 0, [])
        return self.res


    def dfs(self, nums, start, temp):
        self.res.append(temp[:])
        for i in range(start, len(nums)):
            temp.append(nums[i])
            self.dfs(nums, i + 1, temp)
            temp.pop()