LeetCode (Python): 3Sum Closest

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

    For example, given array S = {-1 2 1 -4}, and target = 1.
    The sum that is closest to the target is 2. (-1 + 2 + 1 = 2). 

Solution:

class Solution:
    # @return an integer
    def threeSumClosest(self, num, target):
        num.sort()
        error = float("infinity")
        if len(num)<3:
            return 0
        for i in range(0, len(num)-2):
            begin = i+1
            end = len(num)-1
            while begin<end:
                if abs(num[i]+num[begin]+num[end]-target) < error:
                    error = abs(num[i]+num[begin]+num[end]-target)
                    solution = num[i]+num[begin]+num[end]
                if num[i]+num[begin]+num[end] > target:
                    end -= 1
                else:
                    begin += 1
        return solution