Help on for loop understanding

[Robin Koch]

Am 08.12.2015 um 02:05 schrieb Robert:
> Hi,
> When I learn for loop with below link:
>
> http://www.shutupandship.com/2012/01/understanding-python-iterables-and.html
>
> it has such explanation:
>
> \\\\\\\\\
> for loop under the hood
>
> First let's look at the for loop under the hood. When Python executes the
>   for loop, it first invokes the __iter__() method of the container to get the
>   iterator of the container. It then repeatedly calls the next() method
>   (__next__() method in Python 3.x) of the iterator until the iterator raises a
>   StopIteration exception. Once the exception is raised, the for loop ends.
> \\\\\\\\\
>
> When I follow a list example from the above link, and one example of myself:
>
> //////////
> xx=[1,2,3,4,5]
>
> xx.next
> ---------------------------------------------------------------------------
> AttributeError                            Traceback (most recent call last)
> <ipython-input-76-dd0716c641b1> in <module>()
> ----> 1 xx.next
>
> AttributeError: 'list' object has no attribute 'next'
>
> xx.__iter__
> Out[77]: <method-wrapper '__iter__' of list object at 0x000000000A1ACE08>
>
> for c in xx: print c
> 1
> 2
> 3
> 4
> 5
> //////////////
>
> I am puzzled that the list examples have no next method, but it can run as
> a for loop. Could you explain it to me the difference?

Lists don't have a next method. Their iterators have:

xx.__iter__().__next__()

or

xxIterator = xx.__iter__()
xxIterator.__next__()
xxIterator.__next__()
xxIterator.__next__()
xxIterator.__next__()
xxIterator.__next__()

That's also what your quoted paragraph states:

| It then repeatedly calls the next() method
| (__next__() method in Python 3.x) of the iterator

-- 
Robin Koch