3 sum in Python

class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:
        nums.sort()
        i=0
        ans=[]
        n=len(nums)
        while i<n:
            left=i+1
            right=n-1
            target2=-nums[i]
            while left<right:
                lrsum=nums[left]+nums[right]
                if lrsum<target2:
                    left+=1
                elif lrsum>target2:
                    right-=1
                else:
                    ia=[]
                    ia.append(nums[i])
                    ia.append(nums[left])
                    ia.append(nums[right])
                    ans.append(ia)
                    left+=1
                    while left<right and nums[left]==nums[left-1]:
                        left+=1
                    right-=1
                    while left<right and nums[right]==nums[right+1]:
                        right-=1
            i+=1
            while i<n and nums[i]==nums[i-1]:
                i+=1
        return ans