python学习-迭代器

class MyNumbers:
    def __iter__(self):
        self.a = 1
        return self

    def __next__(self):
        if self.a <=20:
            x = self.a
            self.a += 1
            return x
        else:
            raise StopIteration


myclass = MyNumbers()
myiter = iter(myclass)
for x in myiter:
    print(x)