something go wrongly

[levi nie]

Thanks,
Such methods return None to emphasize that they
do not create new lists.
i got it.
2012/7/8 Chris Rebert <clp2 at rebertia.com>

> On Sat, Jul 7, 2012 at 10:23 AM, levi nie <levinie001 at gmail.com> wrote:
> > my code:
> >
> > aList=[1,2,3,4,5,6,7,8,9,10]
> > xList=[1,2,3]
> > print "now aList is",aList.extend(xList)
> >
> > output:
> > now aList is None
> >
> > what i want is [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 2, 3]
>
> See http://stackoverflow.com/a/1682601
> list.extend(), list.append(), etc. operate in-place, mutating the
> existing list object. Such methods return None to emphasize that they
> do not create new lists.
>
> Regards,
> Chris
>
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