class fibonacci(object): def __init__(self, sequence_count=10): self._first = 0 self._second = 1 self._sequence_count = sequence_count self._index = 0 def __iter__(self): return self def __next__(self): self._index += 1 if self._index == 1: return self._first # 返回数列的第一项 elif self._index == 2: return self._second # 返回数列的第二项 elif self._index <= self._sequence_count: self._first, self._second = self._second, self._first + self._second # 这是 Python 的语法糖，把 self._second 赋值给 self._first ，把 self._first+self._second 的和赋值给 self._second return self._second # 返回数列的第 n 项，其中 n >= 3 else: raise StopIterationif __name__ == "__main__": fi = fibonacci(sequence_count=20) for item in fi: print(item, end=" ")
运行结果如下：
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181