[프로그래머스 Level2] 전화번호 목록 - Python

def solution(phone_book):
    phone_book_set = set(phone_book)

    for phone_number in phone_book:
        for i in range(1, len(phone_number)+1):
            prefix = phone_number[:i]

            if prefix in phone_book_set and prefix != phone_number:
                return False

    return True