__iter__ , __next__の使い方(python)

class calc_Iter:
    def __init__(self, *nums):
        self.ans = nums
        self.nn = 0
        print("init実行")

    def __iter__(self):
        print("iter実行")
        return iter(self.ans)

test = calc_Iter(10,20,30)   #① __init__を実行
print(vars(test))                 #② varsはオブジェクトの中を出力

for i in test:                 #③ __iter__を実行
    print(i)

   ⇒ init実行      #①の実行結果
      {'ans': (10, 20, 30), 'nn': 0}      #②の実行結果
      iter実行      #③の実行結果
      10
      20
      30

class calc_Iter:
    def __init__(self, *nums):
        self.ans = nums
        self.nn = 0
        print("init実行")

    def __iter__(self):
        print("iter実行")
        return self

    def __next__(self):
        if self.nn == len(self.ans):raise StopIteration()
        value = self.ans[self.nn]
        self.nn += 1
        print("next実行")
        return value

test = calc_Iter(10,20,30)    
print(vars(test))      

for i in test:
    print(i)

⇒    init実行
      {'nums': (10, 20, 30), 'nn': 0}
      iter実行
      next実行
      10
      next実行
      20
      next実行
      30