[파이썬][프로그래머스] Lv. 1 완주하지 못한 선수

def solution(participant, completion):
    answer = ''
    
    participant_list = hash(participant) 
    completion_list = hash(completion)
    
    for i in participant_list.keys():
        if i in completion_list.keys():
            if participant_list[i] != completion_list[i]:
                return i
        else:
            return i
    return answer

def hash(data):
    answer = {}
    
    for i in data:
        if i in answer.keys():
            answer[i] += 1
        else:
            answer[i] = 1    
    return answer