Supporting list()

Ethan Furman ethan at stoneleaf.us
Tue Dec 18 00:27:47 CET 2012


Dave Angel wrote:
> On 12/17/2012 09:33 AM, Skip Montanaro wrote:
>> What method(s) does a class have to support to properly emulate a container
>> which supports turning it into a list?  For example:
>>
>>   class Foo:
>>     pass
>>
>>   f = Foo()
>>   print list(f)
>>
>> Is it just __iter__() and next()?  (I'm still using 2.4 and 2.7.)
> 
> I believe the container class needs to define the __iter__() method,
> which has to return an iterator object.
> 
> That (possibly different) iterator class needs both an __iter__() method
> and a next() method.
> 
> If the container class is also the iterator class, which is common, then
> you just need one __iter__() method, which returns self.

The `next()` method is also needed, as `__iter__()` and `next()` are the two methods that make up 
the iterator protocol (`__next__` in python 3k).

~Ethan~



More information about the Python-list mailing list