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Date: Sat, 7 Jul 2012 10:35:49 -0700
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Subject: Re: something go wrongly
From: Chris Rebert <clp2@rebertia.com>
To: levi nie <levinie001@gmail.com>
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On Sat, Jul 7, 2012 at 10:23 AM, levi nie <levinie001@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