test = [1,2]
# 올바른 예시
test += [3] # [1,2,3]
test.extend([3]) # [1,2,3]
test.append(3) # [1,2,3]
# 틀린 예시
test += 3 # TypeError: 'int' object is not iterable
test.extend(3) # TypeError: 'int' object is not iterable
test.append([3]) # [1,2,[3]]
test = ["Lee","Jae"]
test.extend(["Cheol"]) # ["Lee","Jae","Cheol"]
test.append("Cheol") # ["Lee","Jae","Cheol"]
test.extend("Cheol") # ["Lee", "Jae", "C", "h", "e", "o", "l"]
test.append(["Cheol"]) # ["Lee", "Jae", ["Cheol"]]