python 官方WIKI对于iterable与iterator的说明

image.png

1.可迭代(Iterable)对象

from collections.abc import Iterable

class MyIterator(object):
    def __init__(self):
        self.names = list()
    
    def add(self, name):
        self.names.append(name)
    
obj = MyIterator()
obj.add("aa")
obj.add('bb')
obj.add('cc')

print(isinstance(obj, Iterable))

image.png

obj 不是一个可迭代对象

---

from collections.abc import Iterable,Iterator

class MyIterator(object):
    def __init__(self):
        self.names = list()
    
    def add(self, name):
        self.names.append(name)
    
    def __iter__(self):
        pass
    
obj = MyIterator()
obj.add("aa")
obj.add('bb')
obj.add('cc')

print(isinstance(obj, Iterable))
print(isinstance(obj, Iterator))

for x in obj:
    print(x)

image.png
实现 __iter__方法后变为可迭代对象 但是obj 不是迭代器对象，并且
for循环报错iter()返回错误

---

from collections.abc import Iterable,Iterator

class MyIterator(object):
    def __init__(self):
        self.names = list()
    
    def add(self, name):
        self.names.append(name)
    
    def __iter__(self):
        return iter(self.names)
    
obj = MyIterator()
obj.add("aa")
obj.add('bb')
obj.add('cc')

print(isinstance(obj, Iterable))
print(isinstance(obj, Iterator))

for x in obj:
    print(x)

image.png

支持for迭代但是MyIterator依旧不是迭代器

总结：

实现了__iter__方法,并且__iter__方法返回迭代器对象 的类生成的对象即可迭代对象

---

2.迭代器(Iterator)

from collections.abc import Iterable,Iterator

class MyIterator(object):
    def __init__(self):
        self.names = list()
    
    def add(self, name):
        self.names.append(name)
    
    def __iter__(self):
        return iter(self.names)
    
obj = MyIterator()
obj.add("aa")
obj.add('bb')
obj.add('cc')

print(isinstance(obj, Iterable))
print(isinstance(obj, Iterator))

for x in obj:
    print(x)

next(obj)

image.png

一个迭代器(Iterator)对象不仅可以在for循环中使用，还可以通过内置函数next()函数进行调用。

---

from collections.abc import Iterable,Iterator

class MyIterator(object):
    def __init__(self):
        self.names = list()
    
    def add(self, name):
        self.names.append(name)
    
    def __iter__(self):
        return iter(self.names)
    
    def __next__(self):
        return next(iter(self.names))
    
obj = MyIterator()
obj.add("aa")
obj.add('bb')
obj.add('cc')

print(isinstance(obj, Iterable))
print(isinstance(obj, Iterator))

for x in obj:
    print(x)

next(obj)

image.png

总结：

实现了__iter__和__next__方法的类 生成的对象既迭代器