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From: "Lefavor, Matthew  (GSFC-582.0)[MICROTEL LLC]" <matthew.lefavor@nasa.gov>
To: levi nie <levinie001@gmail.com>, "python-list@python.org" <python-list@python.org>
Date: Sun, 8 Jul 2012 20:58:40 -0500
Subject: Re: something go wrongly
Thread-Topic: something go wrongly
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Xref: csiph.com comp.lang.python:25061

If you do want an in-place extension, you could try:

aList=3D[1,2,3,4,5,6,7,8,9,10]
xList=3D[1,2,3]
print "The concatenated lists are:", aList + bList

Though you need to remember that neither aList nor bList is altered in
this situation!


Matthew Lefavor

NASA GSFC [Microtel, LLC]
Mail Code 699.0/Org Code 582.0
matthew.lefavor@nasa.gov
(301) 614-6818 (Desk)
(443) 758-4891 (Cell)





From:  levi nie <levinie001@gmail.com>
To:  "python-list@python.org" <python-list@python.org>
Subject:  Re: something go wrongly



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

On Sat, Jul 7, 2012 at 10:23 AM, levi nie <levinie001@gmail.com> wrote:
> my code:
>
> aList=3D[1,2,3,4,5,6,7,8,9,10]
> xList=3D[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