Python寫乙個物件，讓它自己能夠迭代

仿寫range()物件，物件是可迭代的：

1

#!usr/bin/env python32#
-*- coding=utf-8 -*-34
class
myrange():5#
初始化,也叫建構函式
6def
__init__
(self,n):
7         self.i =0
8         self.n =n910
#類中核心,返回了迭代器本身;
11def
__iter__
(self):
12return
self
1314
#迭代器開始
15def
__next__
(self):
16if self.i 17             i =self.i
18             self.i += 1
19returni20
else:21
raise
stopiteration();
22print(dir(myrange(10)));
23 a = myrange(10);
24print(dir(a)); #
輸出:['__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']
2526
if__name__ == "
__main__":
27     a = myrange(10)
28print("
a*****====>
", next(a)); #029
print("
next a====>
", next(a)); #130
print("
next a====>
", next(a)); #231
print("
next a====>
", next(a)); #332
print("
next a====>
", next(a)); #433
print("
next a====>
", next(a)); #534
print("
next a====>
", next(a)); #635
print("
next a====>
", next(a)); #736
print("
next a====>
", next(a)); #837
print("
next a====>
", next(a)); #938
print("
next a====>
", next(a)); #
發起raise stopiteraion()
39

上面是用next()把迭代器的所有元素乙個乙個依次列印出來的，當然也可以用for迴圈迴圈出來. for i in x: print(i)，然後再用next(a)就會發起raise stopiteration()。下面用列表嘗試一下：

1

#!usr/bin/env python32#
-*- coding=utf-8 -*-34
class
myrange():5#
初始化,也叫建構函式
6def
__init__
(self,n):
7         self.i =0
8         self.n =n910
#類中核心,返回了迭代器本身;
11def
__iter__
(self):
12return
self
1314
#迭代器開始
15def
__next__
(self):
16if self.i 17             i =self.i
18             self.i += 1
19returni20
else:21
raise
stopiteration();
22print(dir(myrange(10)));
23 a = myrange(10);
24print(dir(a)); #
輸出:['__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']
2526
if__name__ == "
__main__":
27     b = myrange(10)
28print(list(b)) #
全部列印出來了,後續沒有元素了
29print("
b===>next b
", next(b)) #
stopiteration.

把迭代器裡的所有元素裝到列表中後，再呼叫next()也會發起：raise stopiteraion.

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