如何使自定义对象可迭代? [英] How to make a custom object iterable?

问题描述

我有一个list自定义类对象(示例如下).

I have a list of custom-class objects (sample is below).

使用:list(itertools.chain.from_iterable(myBigList))我想将所有stations子列表合并"到一个大列表中.因此，我认为我需要使自定义类成为可迭代的.

Using: list(itertools.chain.from_iterable(myBigList)) I wanted to "merge" all of the stations sublists into one big list. So I thought I need to make my custom class an iterable.

这是我的自定义类的示例.

Here is a sample of my custom class.

class direction(object) :
    def __init__(self, id) :
        self.id = id              
        self.__stations = list()

    def __iter__(self):
        self.__i = 0                #  iterable current item 
        return iter(self.__stations)

    def __next__(self):
        if self.__i<len(self.__stations)-1:
            self.__i += 1         
            return self.__stations[self.__i]
        else:
            raise StopIteration

我实现了__iter__和__next__，但似乎没有用.他们甚至没有被召集.

I implemented __iter__ and __next__ but it doesn't seems to work. They're not even called.

任何想法我做错了什么?

Any idea what could I've done wrong?

注意:使用Python 3.3

Note: Using Python 3.3

推荐答案

__iter__是您尝试遍历类实例时调用的内容:

__iter__ is what gets called when you try to iterate over a class instance:

>>> class Foo(object):
...     def __iter__(self):
...         return (x for x in range(4))
... 
>>> list(Foo())
[0, 1, 2, 3]

__next__是从__iter__返回的对象上被调用的对象(在python2.x上，它是next，而不是__next__ －我一般都对它们都使用别名，以便代码可以与任何一个一起使用...):

__next__ is what gets called on the object which is returned from __iter__ (on python2.x, it's next, not __next__ -- I generally alias them both so that the code will work with either...):

class Bar(object):
   def __init__(self):
       self.idx = 0
       self.data = range(4)
   def __iter__(self):
       return self
   def __next__(self):
       self.idx += 1
       try:
           return self.data[self.idx-1]
       except IndexError:
           self.idx = 0
           raise StopIteration  # Done iterating.
   next = __next__  # python2.x compatibility.

这篇关于如何使自定义对象可迭代?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！