이해가 잘 안돼서 찾아보다가 발견한 동영상 입니다.

몇번 보니 이해가 조금(?) 되네요. (머리가 나빠서요 ㅎ)

https://youtu.be/MP-MXkQPrEc

[code]

class Member():
    _ins = []

    def __init__(self, name, height, weight, fat):
        self.name = name
        self.height = height
        self.weight = weight
        self.fat = fat

        self.add_instance(self)

    @classmethod
    def add_instance(cls, ins):
        cls._ins.append(ins)

a = Member("kim", 180, 77, 24)
b = Member("Ihm", 170, 71, 16)
c = Member("Choi", 160, 51, 23)
d = Member("Park", 170, 63, 20)

height_mean = sum([m.height for m in Member._ins]) / len(Member._ins)
print(f"height_mean = {height_mean}")

[/code]