something go wrongly

Lefavor, Matthew (GSFC-582.0)[MICROTEL LLC] matthew.lefavor at nasa.gov
Mon Jul 9 03:58:40 CEST 2012


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

aList=[1,2,3,4,5,6,7,8,9,10]
xList=[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 at nasa.gov
(301) 614-6818 (Desk)
(443) 758-4891 (Cell)





From:  levi nie <levinie001 at gmail.com>
To:  "python-list at python.org" <python-list at 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 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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