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}")