[프로그래머스] 신규 아이디 추천

📖 문제

https://programmers.co.kr/learn/courses/30/lessons/72410

💻 내 코드

def solution(new_id):
    answer = ''
    
    new_id=new_id.lower()
    
    for s in new_id:
        if s.isalpha() or s.isdigit() or s in ['-', '_', '.']:
            answer+=s
    
    while '..' in answer:
        answer=answer.replace('..','.')
    
    
    if answer[0] == '.':
        if len(answer) > 1:
            answer = answer[1:]
        else: '.'
    if answer[-1] == '.':
        answer = answer[:-1]
        
    if answer=='':
        answer='a'
    
    if len(answer)>15:
        answer=answer[:15]
        if answer[-1]=='.':
            answer=answer[:-1]
            
    while len(answer)<3:
        answer+=answer[-1]
        
    return answer