[Level 1] / [Python] 핸드폰 번호 가리기

https://school.programmers.co.kr/learn/courses/30/lessons/12948

프로그래머스

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def solution(phone_number):
    answer = ''
    
    for i in phone_number[:-4]:
        answer += '*'
    
    for i in phone_number[-4:]:
        answer += i
        
    return answer