Python写一个对象，让它自己能够迭代

仿写range()对象，对象是可迭代的：

#!usr/bin/env python3
# -*- coding=utf-8 -*-

class myRange():
    #初始化,也叫构造函数
    def __init__(self,n):
        self.i = 0
        self.n = n

    #类中核心,返回了迭代器本身;
    def __iter__(self):
        return self

    #迭代器开始
    def __next__(self):
        if self.i < self.n:
            i = self.i
            self.i += 1
            return i
        else:
            raise StopIteration();
print(dir(myRange(10)));
a = myRange(10);
print(dir(a)); #输出:['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__next__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'i', 'n']

if __name__ == "__main__":
    a = myRange(10)
    print("a=========>", next(a)); #0
    print("next a====>", next(a)); #1
    print("next a====>", next(a)); #2
    print("next a====>", next(a)); #3
    print("next a====>", next(a)); #4
    print("next a====>", next(a)); #5
    print("next a====>", next(a)); #6
    print("next a====>", next(a)); #7
    print("next a====>", next(a)); #8
    print("next a====>", next(a)); #9
    print("next a====>", next(a)); #发起raise StopIteraion()
    

 上面是用next()把迭代器的所有元素一个一个依次打印出来的，当然也可以用for循环循环出来. for i in x: print(i)，然后再用next(a)就会发起raise StopIteration()。下面用列表尝试一下：

#!usr/bin/env python3
# -*- coding=utf-8 -*-

class myRange():
    #初始化,也叫构造函数
    def __init__(self,n):
        self.i = 0
        self.n = n

    #类中核心,返回了迭代器本身;
    def __iter__(self):
        return self

    #迭代器开始
    def __next__(self):
        if self.i < self.n:
            i = self.i
            self.i += 1
            return i
        else:
            raise StopIteration();
print(dir(myRange(10)));
a = myRange(10);
print(dir(a)); #输出:['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__next__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'i', 'n']

if __name__ == "__main__":
    b = myRange(10)
    print(list(b)) #全部打印出来了,后续没有元素了
    print("b===>next b", next(b)) #StopIteration.

把迭代器里的所有元素装到列表中后，再调用next()也会发起：raise StopIteraion.