merge intervals

def merge(self,intervals):
        sorted_tuple_list,solution_list,index,start = [],[],1,0
        for x in intervals:
            sorted_tuple_list.append((x.start,1))
            sorted_tuple_list.append((x.end,2))
        sorted_tuple_list.sort(key=lambda x:x[0])
        lef,rig = 1,0
        while index < len(sorted_tuple_list):
            #pass all following left type value since we only care about the first left value
            while index < len(sorted_tuple_list) and sorted_tuple_list[index][1] == 1:
                index += 1
                lef += 1
            #pass all previous right type value since we only care about the last right value
            while index < len(sorted_tuple_list) and sorted_tuple_list[index][1] != 1:
                index += 1
                rig += 1
            #consider 1) right value equal to next left value; 2) #left does not equal to #right; if so, we simply go back to repeat
            if index < len(sorted_tuple_list) and sorted_tuple_list[index][1] == 1 and sorted_tuple_list[index-1][1] == 2 and sorted_tuple_list[index][0] == sorted_tuple_list[index-1][0] or rig != lef:
                continue        
            #otherwise we are sure that we found the correct right value of new merged interval and update a new next left index in next loop
            solution_list.append([sorted_tuple_list[start][0],sorted_tuple_list[index-1][0]])
            start = index
        return solution_list