https://school.programmers.co.kr/learn/courses/30/lessons/42577
arr = sorted(arr, key = lambda x : (기준1, 기준2)
arr = sorted(arr, key= lambda x: (len, x)) #1차원 배열일 때
def solution(phone_book):
answer = True
phone_book = sorted(phone_book, key= lambda x: (len, x))
for idx, phone in enumerate(phone_book[:-1]):
if phone_book[idx+1][:len(phone)] == phone:
return False
return answer
txt = "Hello, welcome to my world."
x = txt.startswith("wel", 7, 20)
print(x) #True