python - next = __next__ 做什么？

Question

我看到 next = __next__ 出现在 OOP 代码的多个地方。

这样做的目的是什么？即使没有这条线，它也适用于我。

class Iter:
    def __init__(self, value):
        self.data = value


    def __iter__(self):
        self.ix = 0
        return self

    def __next__(self):
        if self.ix == len(self.data):
            raise StopIteration

        else:
            item = self.data[self.ix]
            self.ix += 1
            return item

    next = __next__

if __name__ == '__main__':
    x = Iter([1,2,3,4,5,6,7,8,9 ])
    for i in x:
        print(i)

Answer 1

这是为了向后兼容 Python 2。根据 What's new in Python 3.0 :

PEP 3114: the standard next() method has been renamed to __next__().